Rust protection

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Introduction

• If you want to invest in your vehicle's longevity, you need to pay attention to rust, even if there is no rust at the moment.
• In some markets and versions the Jimny is galvanised for additional protection.
  • However, even then they tend to rust, especially if the underbody is not regularly cleaned and minor damages cleaned and sealed.
  • Generally speaking, Suzuki vehicles have relatively poor rustproofing from the factory, in line with their relatively low price when new.
• If there is rust, it should be remedied before it gets worse.
• If there is no rust, the surfaces it should be preventively protected while it still has not appeared.
• So, scrape and clean the rust from the underbody of the vehicle (if it has rust), and then protect the entire underbody against future rusting with some good anti-rust material.

Typical points susceptible to rust

Areas of all Jimny generations which are most susceptible to rust (from most common to less common):

1. Body / cabin and suspension carriers (mounting points) on the chassis;
   • Easy to see from underneath after a good wash, unless the underbody had been "protected" (mucked) with bitumen / tar or some other gunk;
2. On Jimnys 3, body just behind front driving lamps;
   • Visible only after removing front wheel arch liners (relatively simple) or removing the head lamps (not so simple);
3. Various factory welding points on the chassis and on the axles as well;
   • Easy to see from underneath after a good wash, unless the underbody had been "protected" (mucked) with bitumen / tar or some other gunk;
4. Body behind the rear bumper (and below rear vertical lamps for Jimnys 3);
   • Visible only after removal of the rear bumper (relatively simple);
5. Boot / trunk floor;
   • Easy to check by emptying the boot.
6. Body floor below the rear seats (and especially where it meets the rear inner wheel arches);
   • Visible only after removing the rear seats (quite simple);
   • Rust usually starts around the threaded holes in the floor for the bolts which secure the rear seats and rear seat belts anchors to the vehicle, and also at the connection points between the floor and rear inner wheel arches.
7. Sills below the side doors (and behind plastic sill covers for Jimnys 3);
   • On Jimnys 3, inner side visible from underneath the car. Outer side visible only after removing large plastic sill covers (risky);
8. Behind side plastic mouldings (claddings), especially around rear wheel arches;
   • Visible only after removing the mouldings (risky).
9. Floor between front seats and the engine compartment;
   • Usually where left front passenger's left foot is located and where right front passenger's right foot is located.
10. Inner wheel arches;
    • Usually rear wheel arches, in combination with rusty floor below the rear seats;

Typical causes of rust

Statistically and generally for any vehicle, the most common "starting" areas where rust begins to develop and progress from further on (most common first):

1. Cavities in the body and in the chassis.
   • These are the most likely areas by far.
   • The reason is that the interior of cavities tends to stay wet for extended periods of time after water gets inside (even if the water does drain through their drain holes), as the interior is concealed from winds, ventilation and heat.
     • If the cavity contains dust, dirt and salt deposits, they will hold moisture for very, very, very long periods of time once they get wet, in some cases never drying out.
       • This is especially true if cavity's drain holes get clogged with filth, preventing any further drainage.
   • Once rust develops in a cavity, it is very difficult or (usually) impossible to eliminate - only to slow down to a certain extent.
     • Therefore, preventive anti-rust treatment of the cavities should be priority number one when combating rust.
2. Welds and panel joints (seams).
   • Welds have a specific metallurgic composition which is highly susceptible to rusting, and require special anti-rust treatment.
   • Panel joints (seams) are points where two or more metal sheets meet or overlap.
     • Moisture usually gets trapped and stays for extended periods of time in such joints if they have not been properly seam sealed.
   • Also, tiny abrasive particles of dust and sand can get trapped in these unsealed joints and overlaps, slowly abrading the paint in them due to vibrations and then exposing bare metal.
3. Threaded holes in the underbody which house a bolt.
   • Moisture gets trapped between the bolt and the hole (inside the threads), rusting both the bolt and the hole itself. Rust then spreads from the hole around to the rest of the body.
   • A typical example in a Jimny 3 are threaded holes in the rear floor for the rear seats and for the front anchors for the rear seat belts.
4. Visible areas of the underbody and of the chassis.
   • These areas are the least likely to become starting points of rust, unless either one of the following conditions exist:
     1. Constantly filthy with filth (especially damp, acidic or salty one) and very rarely washed.
     2. Factory coating damaged by a mechanical impact (rock chip, ground scraping etc.).
     3. Production defect during underbody coating at the factory, so the factory underbody coating cracks or delaminates in certain area(s).
     4. Area with an intentionally thin or non-existent anti-rust coating (except for a primer and paint) from the factory, due to an assumption that the area will not be severely exposed to the elements.
        • Example: Above the gear box, above the fuel tank, etc.
        • The tendency of rust to start in these areas is usually likely only if the vehicle performs deep water wading or deep mud / snow plowing.

Illustrations of typical rust points

Body carriers on the chassis

• An example of a severely corroded Jimny 3 underbody. The vehicle was 10 years old with only 60 000 km on the odometer, mostly on paved, salty alpine roads!
• 

  This chassis rail is severely weakened

• 

  This is a critical structural failure, and prevents the vehicle to be licensed for road use

Area behind the head lamps

• Area behind the head lamps is a typical rust point on Jimnys 3, like in this standard example.
• 

  View from the front, after the head lamp is removed

• 

  View from the back, after the front wheel inner arch liner is removed

• Significant welding effort is required to properly repair the rust in the tricky place behind the head lamps.
• 

  View from the front

• 

  After sealing the seams and painting

• 

  View from the back

• 

  After sealing the seams and painting

Front floor sections below side door window moving controls

There is a double floor panel in this area of the vehicle (both on the left and on the right side), and it usually rusts from the inside of that body cavity. The only possible preventive measure is to spray wax inside that cavity by accessing it from the underside of the vehicle. However, the only factory drain/access hole is very small and might need widening with a drill or a round filein order to be able to put a spraying hose through it ...

• 

  Front right floor section, roughly where right front passenger's right foot stands. Vibrodamping bitumen sheets had been removed prior to taking this picture.

Rear floor section including boot

• 

  Floor below the rear seat bench, with bitumen vibration damping compound removed

• 

  Severely rusted boot floor. Someone desperately applied wax to save it - too late and from the wrong side!

• 

  Properly and thoroughly rusted rear floor - the boot floor has already been cut off

• Salvage efforts on a thoroughly rotten rear floor section
• 

  Weld after weld after weld after weld

• 

  Notice that the entire boot floor has been replaced with a flat sheet

• 

  A lot of space has been lost by using a flat boot floor sheet

• 

  Painting then seam sealing

• 

  Close-up after work is done (note: vibrodamping materials are now missing)

General idea

There are several schools of thought regarding which materials and methods should be used to achieve anti-rust protection.

There are generally five types of coatings which are applicable to underbody rust protection:

• Bitumen or tar based (the oldest and cheapest type);
• Synthetic rubber / plastic resin based;
• Waxes;
• Polyurethanes;
• Lanolin (sheep wool wax) based;
• Multi-mix compounds (primer + stiff anti-chipper + paint in one);

Whichever coating type you choose, beware of the following risk factors:

1. It is of paramount importance to eliminate the last atoms of rust from the surfaces which are to be coated.
   • Any remaining rust behind the coating will spread again like cancer, and its advance will even be accelerated because it is concealed and undisturbed.
   • Rust should be first mechanically removed, and then the remaining microscopic traces chemically eliminated.
2. The coating has to be properly applied according to manufacturer's guidelines, and the underlying surface has to be completely clean (and sometimes sanded/roughened for better adhesion).
3. If the above two conditions are not properly met, there is a high risk that the coating will de-laminate or crack in the long term, thus allowing moisture to creep under it.
   • This will severely corrode the underlying metal, as the moisture under it is trapped and never dries off, so the corrosion can thrive under.
   • The worst thing is that this will be invisible to the unsuspecting happy owner.

The perfect rust protection method

Separating body and the frame

• In general, the best results by far can be achieved if the vehicle is first dismantled (body completely separated from the frame).
• However, that is a major undertaking by itself and can be quite an unpredictable process with older vehicles.
  • There will be many seized bolts which break off, some flaky brake lines which crack during removal, some stuck bolts in the bushings will require replacing the bushings, etc.

• The main benefit if the body is separated from the frame (and the transmission and the suspension, which remain on the frame) is that the underside of the body can be thoroughly cleaned and protected, as well as the top of the frame/chassis.
• When the body and the frame are separated, it is then quite convenient and accessible to completely sand blast every square centimeter of the underbody, chassis and all suspension and transmission components.
  • Sand blasting is the most thorough method of removing all rust and most prior coatings.
  • However, sand blasting does not effectively remove prior coating if it is an elastic compound (for example bitumen which is still elastic).
    • The only two effective methods to remove elastic compounds is to either heat them up and manually scrape them off (messy) or to extremely cool them down (with "dry ice") and then chisel them off while they are brittle.

Dismantling everything from the frame

• The dismantling of the underbody can be taken further to the "complete/perfect" level by also dismantling all the engine, transmission and suspension elements from the chassis.
• Then the bare chassis (and various suspension elements) can be dipped into a hot zinc bath ("hot zinc plating" process).
  • This is the only method which cleans and protects the inside of the chassis tubes and rails.
  • There is no other solution for the complete chassis protection.
  • Beware that hot zinc plating can be risky, as the chassis might distort due to high temperatures in the bath (something around 450-500 degrees C).
    • Check this with your hot zinc plating facility beforehand!
• Another method is cold zinc plating - dipping the metal into a cold zinc bath and applying electricity throughout (also galled zinc galvanization).
  • This method imposes no risk for the treated parts.
  • However, cold zing plating is thinner and can be applied only to the exterior surfaces of the chassis and other hollow objects, not to the interiors.
• Note that the process of both hod and cold zinc plating usually implies prior dipping of the material to be treated into a pool of special acid, which kills of any remaining rust, dirt, greases and bad spirits.
  • This is usually included in the price of zinc plating, but ask the zing plating facility first!
• Of course, each dismantled suspension piece can also be taken for zinc plating or some other coating.
  • However, the bushes have to be removed first from radius arms, panhard rod arms, anti roll bars, etc.

• After a vehicle component is zinc plated, it can then be treated with a "final" coating.
• There are several materials which can be used.
  • For example: automotive wax, bitumen-alike coating, plastic-alike coating (not recommended for outdoor applications), lanolin, polyurethane ("bed-liner") coating, etc.
• It is better to apply some final coatings in two thinner passes (layers) than in one thick pass.
• Opinions on which final coating material is the best vary as much as do opinions on an only proper world religion.

The ordinary rust protection method

General description

• Dismantling half of the vehicle is neither time nor cost effective for most people.
• A standard rust protection method does not involve dismantling of any part of the vehicle.
• Instead, it relies on the principle "do what you can do from underneath".

The disadvantages of the ordinary method are:

• No type of zinc plating can be performed.
  • Pressurized zinc spray cans are (allegedly) much inferior solution to proper zinc plating and they should (allegedly) not be used. It's allegedly better to use a proper primer paint on bare metal.
• Mechanical rust removal techniques (both wire brushes and sand blasting) can not be nearly as thoroughly performed.
  • For example, it is almost impossible to treat the upper surface of the chassis, and access to many "secluded" areas of the underbody is physically restricted, or risky because of brake and fuel lines, vacuum pipes, wires, etc.

"Enhancing" the method

• For Jimny 3 at least, the limited accessibility issue of the ordinary method can be significantly reduced by undoing all 8 bolts which secure the body to the frame and then slightly temporarily jacking up the body.
  • This is the same procedure as when installing a body lift.
    • It is known that 2" (5 cm) body lifts are trivial to install to a Jimny 3, as they don't require extending brake lines, vacuum pipes, etc.
  • It has been confirmed that a Jimny 3 body can be temporarily jacked up to 4" (10 cm) from the frame just if you disconnect the brake lines from the frame (not from the wheels!).
• You will need 14 mm deep hex socket for the front body mount bolts and 17 mm deep hex socket for the rear body mount bolts.
  • Spray the bolts with copious amounts of WD40-alike fluid in at least a few iterations a couple of days before.
  • You will probably need significant force and leverage to undo the body mount bolts if the Jimny is relatively old or rusty.
• Temporarily raising the body by 5-10 cm from the frame gives sufficient access to most hardly accessible areas, like the body above the fuel tank and above the transfer case, top side of the chassis, etc.
• When the body is jacked up, it is easy to access the top of the body-to-chassis bolt mounts, and properly clean them and protect them.
  • These are inaccessible otherwise and tend to rust heavily, and then spread the rust to the rest of the body mounts, which then cause a structural failure of the car!

• The other way to gain access to hardly accessible parts of the body are to remove the fuel tank, the rear exhaust muffler, and/or the transfer case.
  • Removal of the fuel tank will provide much better access to the underside of the body below the rear seats and below the boot.
    • In practice, it is usually not required to remove the fuel tank completely, but just to lower it slightly in order to gain wider access to the underbody above it.
  • These are the areas which usually suffer the most from rust on Jimnys, and these areas can then be properly cleaned and protected.

The wiki article "Fuel tank removal and installation" contains a guide on how to lower and even remove the fuel tank.

Cleaning and washing

Importance

• Unless the vehicle is bran' spankin' new from the factory, its underbody has more layers and varieties of dirt and filth stacked onto it than there are galaxies in the universe.
  • This is valid even if you wash it regularly.
• Removing all the contaminants from the surface to be overcoated is of paramount importance, as the long term adhesion of the coating to be applied critically depends on the cleanliness and roughness of the underlying surface.

Washing agents

• Most detergents and degreasers do not have the capability to thoroughly clean the surface of the underbody, due to a phenomenon of composite "fused" dirt called "traffic film".
• Although regular power washing with a common degreaser removes all mud, dirt, sand and common filth from the underbody and makes it appear clean, the final layer of traffic film stays on firmly on the surface.
  • The only way to convince someone that traffic film is still present on an apparently clean surface is to let them see the same surface again (in a very different color) after the traffic film has been removed from it.
• Traffic film is so tough to remove that the only adequate chemicals for its removal are specialized detergents and degreasers, which explicitly state that they remove traffic film (hence called TFR - "traffic film remover").
  • Many people have tried hard with various "non-TFR" detergents and degreasers, and the success is minor at best even with extreme effort and persistence.
  • Even with a TFR, you might have to power wash the vehicle several times in order to completely remove traffic film.
• Only after traffic film is removed from the underbody, you will really see how it used to look like when the vehicle left the factory.
• TFRs are rather strong chemicals which can damage paint if used in high concentrations.
  • Therefore, beware what you wash with which concentration of TFR, and make certain that you rinse it of thoroughly.
• Note that the "strength" and/or quality of TFRs vary between manufacturers or even among their products.
  • For washing the underbody, it would be the best to use a stronger variant of TFR (or a relatively high concentration of it if allows for several dilution ratios).

• Power washing with hot water is significantly more effective than with cold water, but requires relatively expensive power washing machines and willingness to spend plenty of energy.
• Some detergents or TFRs do not like hot water.

Proper washing procedure

1. Check the underbody first for any thick / heavy sediments of baked mud, stuck or glued grass or branches, etc.
   • Remove those heavy deposits manually to enable better penetration of the liquids to the underbody itself during power washing later.
2. Remove the drain plugs from all the cavities.
3. Wash the cavities with a general purpose automotive detergent / degreaser and then rinse them off thoroughly.
   • Repeat this step at least twice.
4. Temporarily reinstall the cavity drain plugs.
   • This will prevent most of the detergent from entering the cavities during underbody washing.
5. Power wash the underbody first with a general purpose automotive detergent / degreaser in order to remove the main / common mud, dirt and filth.
   • This will decrease the consumption of a TFR later on (which is more expensive), and allow better penetration of TFR directly onto the exposed traffic film layer.
6. Rinse the underbody with clear water.
7. Soak the underbody with a TFR.
8. Thoroughly rinse the underbody again.
9. Since the underbody probably will not be 100% clean after the first pass of TFR, repeat the previous two steps one more time.
10. Remove the cavity drain plugs again.
11. Finally, you must allow or force the washed surfaces to dry off completely before you coat them.
    • Hidden, indented or concealed surfaces can take much more time to dry.

Cleaning and washing the cavities

General explanation

• Anti-rust treatment of the cavities in the chassis and in the body is even more important than the treatment of the exposed areas of the underbody.
  • This means waxing them with a cavity wax, but before that, it involves cleaning the cavities with brushes (where possible) and then either blowing them with compressed air or a strong leaf blower, and/or (power) washing them.
    • If cleaning a cavity with brushes is not feasible (unreachable or a very small access hole), then just power wash it well.
• It is best to clean / wash the cavities before washing the underbody.
  • This way, the dust or muck that exists /drains from the cavities will not contaminate the freshly cleaned underbody.
  • Cavities will also have more time to dry while you are busy washing the underbody.
• Don't forget to remove all drain plugs from the cavities before blowing or washing them.

Inspecting the cavities

• The exact condition of cavities can be determined by performing a probing inspection using an endoscope camera.
• Such equipment (in its "hobby" quality / performance level) is quite affordable these days and available even from generic online shops like Ebay, Amazon, Aliexpress etc.
• An endoscope camera is a very small camera which is embedded inside the end of a flexible cable (together with illuminating LEDs), usually minimally bulging on its end.
• The other end of the cable can either have a USB connector for direct connection to a computer, or have a special connector for connection to its own control / viewing module.
  • The 1st type of camera can be used with almost any PC with the provided software.
    • Some even present themselves to the operating system as a standard web camera, which can be viewed in any program which utilizes web cams - for example in Skype.
• The 2nd type of camera has its own (usually battery powered) control / recording module with a small display.
  • Therefore, it works independently and is more portable.

• By inspecting the cavities with an endoscope camera, it is possible to determine the exact locations of any rust spots, and then direct the brushing / scraping efforts at that particular location, as well as waxing efforts.
  • It is relatively easy to calculate the distance from the entry point into the cavity to the location of a rust spot in it just by measuring the length of the endoscope cable which went inside until it reached the spot, and then apply the same length when inserting a brush / scraper / washing hose and also a waxing hose later on.

Brushing or scraping the cavities

• It is recommended to manually brush the cavities which have relatively large access holes prior to washing them, in order to partially scrape off and release the accumulated and hardened dirt and dust inside of them.
  • This will significantly improve washing efficiency, since it is near impossible to effectively power wash the cavities, because a water jet can rarely be directed at their surfaces perpendicularly in order to attack the hardened dirt or mud deposits.
  • It is best to use long cylindrical brushes, like the ones designed to clean ventilation pipes or even chimneys.
    • Such brushes should be available in any home improvement store, or even in generic supermarkets.
    • Beware when using very abrasive brushes (usually the ones with metal wires or metal nets, intended for cleaning chimneys), as they will damage paint inside the cavities.
      • However, if the cavity is already rusty (usually the case with the chassis rails), than this kind of brush is actually a good tool to remove some of that rust.

• In case of rusty cavities (for example usually the case with chassis rails), brushing is rarely near enough strength to scrape off the rust.
  • A far "stronger" mechanical rust demolition method is required.
    • However, the constrained and hard to reach nature of cavities requires quite a bit of ingenuity and improvisation to effectively perform the mechanical rust scraping.

An example effective improvisation method is:

1. Connect a braided steel cable to an electrical drill;
2. Put the cable through a flexible cable conducting pipe;
   • This will prevent the cable from twisting around and tangling up when operating;
3. Properly secure one or two pieces of chain to the other end of the cable;
   • Roughen up the chain's surface (make it jagged) with a very coarse sand paper, a file or even an angle grinder.
4. Put the assembly into a cavity as far as it will go.
5. Operate the drill, while carefully slowly pulling the cable out of the cavity;
   • The chain(s) will be beat around viciously against the walls of the cavity, taking off most of severe rust.
6. Repeat the last two steps several times until most of the heavy rust is removed from the cavity walls.
7. The removed rust piles can then be vacuumed from the cavity by a vacuum cleaner or blown out from the cavity with compressed air or with a leaf blower.

Since a video explains it better than a million words, here are two example videos of DIY rust elimination from cavities:

• Video 1
  • The only "mistake" that the operator in that video did was using a bare braided cable - not putting the cable through a flexible cable conducting pipe.
• Video 2

On Jimnys 3 at least, the cavities with access holes large enough for long cylindrical brushes are:

1. Chassis rails and tubes;
   • These usually have the most amount of the most stubborn dirt inside of them by far compared to all the other cavities;
     • These usually have at least some rust at least on certain points.
   • Read more in the rest of this article on how to remove rust from the insides of a rusty chassis.
2. Below / behind rear vertical lamps;
   • Accessible when rear seat belts are removed;
3. Side door sills;
   • Accessible through holes which house the rear speakers (between side doors and rear seats);

Washing the cavities

• The most important cavities to wash are the interiors of the chassis rails and tubes.
  • This includes both longitudinal rails and all transverse tubes.
  • They should be washed and rinsed multiple times, while pushing the washing hose through them all the way front and back multiple times and by twisting and tossing the hose around inside of them while doing so.

• Some power washing machines have an option of attaching special nozzles / heads (usually from the same manufacturer), which are designed to be inserted into cavities and manipulated inside (rotated and moved around) while the washer is operating.
  • Even if such accessories are not available, the high pressure water output hose from the power washing machine can be inserted into most cavities without any head attached to it, and then manipulated (tossed around) while it is inside and the machine is running.
• Using TFR to wash the cavities is generally not needed (except perhaps for the chassis), as the usual contaminants which form traffic film hardly get inside of them.
  • Therefore, a standard automotive detergent / degreaser should suffice.
• Rinse the cavities with plenty of clear water, in order to insure that no degreaser or detergent remains inside.

Drying the cavities

• Allow for an extended amount of time for the washed cavities to dry - at least several days is preferred.
  • It takes much more time for them to dry than for surfaces exposed to the outside world, even during a hot summer day.
    • This discrepancy is even much more pronounced during colder weather.

Methods to reduce the time needed to dry the cavities:

1. Blow the cavities with plenty of compressed air.
   • It is preferred to use an oil-less air compressor or oil-lubricated air compressor with an oil filter in the output line, so that the compressed air does not contain oil droplets, which will contaminate the surfaces which are being dried.
2. Use a hot air gun or an ordinary hair dryer.
   • Take care not to blow hot air onto a single point for an extended period of time, or it might overheat the paint on that spot.
   • This method is difficult to apply to cavities which have small access holes.
3. Use a leaf blower.
   • These machines are particularly useful for long cavities like the chassis rails.
   • It is also a good idea to blow through a chassis rail with a leaf blower after brushing or scraping the dirt inside of it and prior to washing it.
   • This method is difficult to apply to cavities which have small access holes.

Importance of existing rust removal and bare metal surface etching

• Maximum effort should be applied towards the removal of the existing rust.
• Rust is like cancer.
  • If even a tiny untreated bit remains, it will spread again all around in due time, especially if covered with something so it can work undisturbed.
• Equally as important as thoroughly removing all the rust from a surface is thoroughly roughening / keying / etching the healthy underlying surface to enable strong and long lasting adhesion of the first (direct to metal) paint coating.

• A standard method of rust removal is by using manual or powered wire brushes (attached to drills, grinders, etc.) or sand paper.
• Much more thorough rust removal can be accomplished only with sand blasting.
  • Typical case where sand blasting excels over wire brushing is elimination of rust from pits, grooves etc (heavy pitted rust).
    • Removing specks of rust from pits is quite difficult otherwise.

• Very rough and completely clean surface finish is required for proper adhesion of any primer paint coating over bare metal.
• The additional (extremely important) effect of sand blasting is that it also inherently thoroughly keys / etches / scars the underlying healthy surface (onto which the paint will be applied).
• If the rust is removed using wire brushes, the clean underlying surface then has to be additionally roughened / keyed / etched for proper primer paint coat adhesion, because wire brushing does not leave nearly rough enough surface (it even tends to polish it).
  • Polished surface is quite the contrary to what any paint coating needs for proper strong adhesion.
  • Roughening of the surface after wire brushing is usually done with 150-250 grit sand paper (two passes - second pass perpendicular to the first pass).
    • This is the minimum surface roughening level required for any hope of long lasting proper paint adhesion, but a proper sand blasting will always create a profoundly rougher surface.

• If tiny specks of rust still remain after the rust removal (usually in the pits after wire brushing), the treated surfaces should then be "painted" over or sprayed over with some chemical which dissolves rust.
  • Its job is to dissolve the last tiny thin remains of rust which have stayed in some pores or scratches after the mechanical removal has been performed.
  • A rust treatment chemical usually needs some time (counted in minutes or even hours) to do its job.
• Popular chemicals for this purpose are phosphoric acid and hydrochloric acid.
  • Inform yourself of characteristics and hazards of any acid which you intend to use, especially hydrochloric acid!
  • Hydrochloric acid makes a quick genocide of the rust.
  • However, it also eats away good metal too, and its vapors can corrode surrounding metal as well as your eyes and lungs if used indoors.
    • If that does not scare you enough, know that it may also cause your penis to fall off.
    • One positive side effect of its metal eating capability is that it will also etch / roughen the metal which it eats, making the surface more suitable for the future primer coating.
  • Hydrochloric acid should not be used on any metal which has a structural bearing role (for example: chassis, tow bar, suspension arms, etc.), as it causes a fatigue in the metal due to the effect called "hydrogen embrittlement".
• Some rust elimination chemicals require rinsing them off with a suitable liquid after a certain amount of time, or even grinding them off after they harden off, while others allow further coating applications.
  • Even with those chemicals which allow subsequent overcoating, it is much better to remove them from the metal (after they had done their job) and then coat directly on top of bare metal.
    • Reason: It is always better to apply a primer directly onto bare metal instead onto some intermediate coating of inferior adhesion properties.
      • In other words - no rust elimination chemical can be a good coating layer!
• Note that most of these rust elimination chemicals do not seal the surface against future rusting!
  • If you don't further treat/coat the surface just after the chemical has done its job, new rust will develop on it soon!

• The process of roughening the surface with sand papers after wire brushing should be performed after the rust elimination chemical has done its work and after it has been rinsed off and the surface has dried.
  • This way, the sanding will also remove any remaining dried parts of the rust elimination chemical.

• A common misconception is that the best chemicals for eliminating rust are the so called "rust converters" - the ones which chemically alter (transform) the rust into another non-ferrous material (making it impotent).
  • One of the reasons for the misconception is that such chemicals are usually much more expensive than ordinary "rust melting / elimination" chemicals, so people go by the logic "what's expensive is supposed to be effective".
• Use of magical "rust converting" chemicals should be strongly avoided.
  • They are usually some form of tannic acid.
• To make the elaboration simple, two main reasons against tannic acid are:
  • It rarely penetrates the rust more than its shallow surface, thus leaving its inner layers untouched.
    • Don't believe this?
    • Then apply this kind of chemical to a rusty surface and wait for it to finish its job as specified by the manufacturer of the chemical.
    • The color of rust will probably change from brown/orange to black or dark blue or similar.
    • Then scratch the surface with a sharp knife or a sharp nail.
    • The scratch will most probably reveal the good old brown/orange rust below the converted top layer.
  • The converted top layer of rust prevents the corrosion inhibitors, which are usually a part of a subsequent coating like a wax or a paint primer, from performing their job.
    • Reason: The converted layer behaves like a barrier between the corrosion inhibitors and the inner layer or rust under it, enabling the rust to still thrive under.

Timing and weather protection

• Note that timing and weather protection is important during the entire rust proofing process.
• For example, if you sand blast a metal surface, and then load it onto a trailer to be taken somewhere else for the painting, if it's a cloudy day with high humidity (let alone rainy day!), the metal will quickly develop rust flecks ("flash rust") on the way to the next station.
• The rougher a bare metal surface, the more susceptible to flash rusting it is (that's the nature of things).
• Also, if you wait too long after the application of the rust treatment chemical, the chemical will "evaporate" and the rust will return from the air moisture again ....
• It is also important to obey manufacturer's curing times and environmental application temperatures for each used chemical product.
  • It can be equally bad if you apply something over a a product too early (before it has cured) or too late (after it has completely hardened).
    • In both cases, the next coating might not adhere properly to the first one, creating a significant risk of de-lamination in the long term.
  • It is for this reason important to carefully observe and plan when buying various chemical products, because some products' overly quick or overly slow curing times or restrictive temperature range can complicate your working schedule and timing.

• Most primer paints are porous, meaning that moisture passes through them.
  • An important exceptions to this are epoxy primer paints.
    • That is one of the reasons why epoxy primer paints are the preferred type of primer coating for high quality rust proofing treatments.
• If a primer coating is porous, you need to apply final coating(s) of your choice (which need to be airtight) as soon as the primer paint dries off.
• A lot of people leave the project for a while (maybe to take a rest or a vacation) after the application of a primer paint, thinking that they have covered the bare metal and how the main "rust shield" is on, but it probably isn't!
• Most primer paints provide no protection against moisture, they are just a "stop-gap" layer so that the final airtight coating can adhere properly!

General procedure of underbody rust proofing

1. Thoroughly wash and rinse the underbody multiple times, first with a standard automotive detergent and then with a traffic film remover chemical.
   • It might be possible to arrange the service of washing the vehicle underbody with some mechanical or body repair workshops which have vehicle service lifts.
     • Washing the vehicle underbody when it is lifted 2 meters up in the air provides the best approach for quick and thorough cleaning.
2. Let the underbody dry off completely.
   • This may take even a few days, depending on current weather conditions.
3. Thoroughly check all sections of the underbody, with special attention to factory or additional welds, hidden areas, etc.
   • Pay attention to any sign of existing coating becoming delaminated, cracked or peeled off.
   • Mark around each found problem area so that you do not miss it in the later process.
4. Remove all plugs which seal cavities (like plugs on chassis rails, door sills, etc.).
5. Mechanically remove any rust or peeling/cracked old coatings.
   • Use hand wire brushes, power drill or angle grinder mounted wire brushes, sand blasting, etc.
   • Sand blasting is by far the best / most thorough method for multiple reasons, but is dirty and expensive.
   • Pay attention not do damage any cables, hoses, wires, etc.
6. Cut out any critically rusted areas and weld in new pieces of metal sheets.
7. If there are any localized specks of rust still remaining which can not be eliminated mechanically, you need to eliminate them chemically.
   • Use rust elminating acids, like phosphoric acid or even hydrochloric acid.
   • Inform yourself of characteristics and hazards of any acid which you intend to use, especially hydrochloric acid!
8. Using sand paper in multiple directions, abrade / roughen up any non-sandblasted bare metal surface or painted metal surface which you intend to overcoat.
   • Reason: any new coating adheres much better on a rough surface than on a smooth surface.
   • This step is especially important in case of bare metal surfaces which had been wire brushed, as wire brushing tends to polish them.
9. Clean and degrease the all parts of the underbody which had been exposed to dust or other contaminants during the previous activities and let dry completely.
10. Apply one coat of primer paint on all bare metal surfaces.
    • This includes any bare metal welds or bare metal panel joins.
    • See more info below on best primer types.
11. Apply seam sealant to all previously rust-treated areas which have welds or where two metal parts/panels join together.
    • It is best to use a polyurethane seam sealant - the more expensive, the better.
    • The welds and panel joins should have one layer of cured primer coating over them prior to the application of the seam sealant.
12. Now apply the 2nd coat of the same primer paint over all surfaces which had been coated two steps before.
    • This includes painting over the cured seam sealant.
13. On surfaces with existing healthy protective coating, you might need to apply a solvent to "prepare" the surface for further coatings.
    • This depends on the type of existing coating and the type of the anti-chip coating to be applied.
14. Apply a stonechip coating of your choice (bitumen-based, synthetic rubber based, polyurethane, etc.) to the entire underbody.
    • There are various types of stonechip coatings, with various long-term durability - investigate on your own!
    • It is better to use a spray gun instead of brushes because of less chance of having non-covered micro-spots.
15. Apply underbody wax over the stonechip coating.
    • This is optional, but it provides additional flexible layer of protection, which can self-heal when a rock hits it.
    • It is better to use a spray gun instead of brushes because of less chance of having non-covered micro-spots.
16. Apply cavity wax in all cavities (inside the chassis rails, inside door sills, inside doors, inside anything that is hollow.
    • Use the holes, which you had exposed earlier when removing the plugs, as entry points.
    • Use a spray gun with special long tube with multiple side-facing nozzles on its end.
17. After wax spraying is complete and everything else has dried out, return all plugs into position and seal them with raw rubber.
18. Take a vacation.
    • Preferably in an air spa to clean your lungs of all of the consumed fumes from all these poisons.

Choice of coating types

General overview

• There is no single coating type which is equally suitable for the entire underbody.
  • For example, a coating for inside the cavities like inside the doors has to be different than the coating on the wheel arches.
• Therefore, multiple coating types need to be used on different parts of the underbody.

• There are numerous schools of thought / beliefs on which type of coating is best for anti stone chip protection in the exposed areas of the underbody.

Primer paint

In case that there is bare metal to protect, a primer paint is necessary no matter what subsequent / final coating is to be applied.

The best primer paints are the ones which contain all of the following properties (from most to less important):

1. Epoxy;
2. "High build";
3. 2-component ("2K");
4. Anticorrosive;

The main advantages of epoxy over other types of materials are:

1. Exceptional toughness (resistance to impacts and abrasion);
2. Very good resistance to temperature, chemicals and mechanical stress;
3. Non-porous;
   • Does not allow water or moisture through.
   • This is especially important when leaving a primer painted metal surface overnight (or for multiple days) before applying further coatings to it.
     • This is usually the case in practice.
4. All these properties enable most epoxy primer paints to also serve as final / top coat paints (officially endorsed by their manufacturers) as long as they are not exposed to UV rays from the Sun.

The disadvantages of epoxy paints:

1. Usually quite toxic to work with;
2. Very difficult to remove after they cure;
3. Relatively expensive;
4. Do not like exposure to the Sun (UV rays);
   • Irrelevant for the underbody applications.

About the "high build" property:

• "High build" means that the paint is designed to have a relatively high dry film thickness.
• In other words: designed to be applied in a rather thick layer.
• High thickness further increases coating's flexibility and toughness.
• "Dry film thickness" refers to the thickness of the applied coating after it cures.
• Generally, every coating is designed for a certain range of DFT.
  • It is equally bad to apply it thinner than the designed DFT range as it is to apply it thicker than the designed DFT range.
  • When the applied DFT is too high, it usually causes the coating to crack later on.
• For example, the optimal DFT of common "regular" epoxy primers is around 20 to 80 micrometers, while the optimal DFT of common "high build" epoxy primers is anywhere from 150 to 500 micrometers or more!
• Another advantage of many "high build" primer paints is that many of them are designed to be applied by brush or roller, which is not the case with "regular" primers (as those two methods always achieve high DFT).

About 2K:

• "2K" usually means that the paint comes in two components / parts - the base and the hardener - and the two must be mixed together in a certain ratio before the application.
• The general rule is that a 2K paint will always have better chemical and physical properties (longevity, etc.) than a 1K paint.

About anti-corrosive properties:

• Anti-corrosive primers are those which contain rust inhibiting chemicals.
• Such chemicals interact with any remaining rust on the bare metal surface and slow down its progress.
  • It is always better to have zero rust on the bare metal surface to be coated, in which case no rust inhibitors are needed.
  • However, if that can not be achieved, than rust inhibitors in the primer coating are the 2nd best weapon to have.

Product examples:

• An example of a popular and long time proven high build 2K epoxy primer paint is Jotun Jotamastic 87.
  • An industrial coating used for coating bridges, off-shore oil refineries, liquid tanks, girders, etc.
  • Quite popular among enthusiast restorers of old timer vehicles.
  • Can be applied by roller or by brush, as well as by a high pressure airless spray gun.

Bitumen / tar

• Bitumen / tar based products are the oldest and still the most popular type of general purpose underbody rust protection (predating automobiles).
• They are sometimes called "rubberized coating" (especially in USA), but this classification is not synonymous, as there are synthetic rubber coatings and vinyl coatings which could also be classified as "rubberized".

Advantages:

• Very cheap;
• Simple to apply;
• Have exceptionally high dry film thickness;
  • They are therefore quite elastic and even provide certain sound and heat insulation;
• Their elasticity and thickness combined give them exceptional resistance to abrasion and chipping when rock impacts or scraping occurs.
• Can usually also be applied by brush (not just by a forced air gun).
• Impossible to wash off with power washing.
• Excellent choice of underbody coating when attempting to hide existing rust and damage prior to selling the car and presenting the car as "protected from rust" to naive customers.

Disadvantages:

• Do not tolerate heat, so should be avoided in the engine compartment, near the exhaust pipes, etc.
• Such coatings tend to lose their elasticity over time (sooner or later), when they become brittle and develop cracks or (more commonly) start to delaminate from the surface.
  • Since they are usually very thick, local cracks and delaminations are usually very hard or even impossible to spot, thus staying undetected for a long time.
  • When they crack or delaminate, they trap moisture and salts between them and the surface which they are supposed to protect, rapidly accelerating its demise.
    • A metal "protected" by bitumen can rust several times faster than if it had been left bare and exposed to the outside environment!
• Bitumen and tar tend to delaminate more if the underlying surface onto which they had been applied has not been cleaned properly of dust, grease or previous rust and then properly roughened.
• It is impossible to detect a deteriorating / rusting metal surface behind such coatings due to their thickness and elasticity, until most of the metal behind the bitumen gets so rotten that the entire metal panel collapses.
• If applied clumsily or without proper protection of areas which should not be coated (bolts, springs, bushes, pipes, hoses, moving parts like the drive shafts, etc.), they will "gunk up" the underbody and make any future servicing job a very miserable one.
  • Many mechanics refuse to service the drive train and the suspension of such vehicles.
    • Nobody should blame them for such policy.
• They are extremely difficult to remove, with lots and lots and lots and lots and lots and lots and lots and lots and lots and lots and lots and lots of tedious manual labor required.
  • Sand blasting is usually completely ineffective, as bitumen and tar are exceptionally resistant to abrasion.
  • Also completely ineffective are any wire brushes and sand papers, as the bitumen rapidly clogs them up.
  • Chemical removal methods do work, but they require a lot of liquid and kilometers of rags to wipe the melting gunk off.
  • In the end, the most effective method is a chisel and a hammer during as cold day as possible (to have the bitumen as brittle as possible), with inevitable damage to the metal due to chiseling.
  • Pro tip: It is best to delegate the bitumen removal job to convicts, prisoners of war or feminists.

• An example video from USA says more than a thousand pictures, each of which says more than a thousand words.
  • The video portrays the fate of a 4WD vehicle which had been "protected" by a bitumenous rust proofing coating product called "Ziebart", which is quite popular in certain parts of USA.
  • That coating had been applied to that vehicle when the vehicle was new.
  • The author stated that the vehicle was less than 10 years old when the video was made, but they did not state its exact age (guessing somewhere between 5 and 8 years old).

Conclusion:

• Strongly avoid using bitumen or tar based underbody coatings, due to high risk of accelerated failure and the extreme difficulty of removing the coating.
  • While the applied bitumen / tar coating typically looks pristine for years and years after the initial application, the protected Cinderella's carriage might suddenly turn to a pumpkin after the invisible rusty deadline rings!
• The only parts of the underbody where a bitumen based coating might make sense is the wheel arches, which are the most stone-chip exposed areas of the underbody by far, and also create the most noise when driving on gravel or through mud.
  • But even for this application it is better to use something more expensive.

Wax

• There are several types of wax-based materials which are suitable as underbody protection coatings.
• They are usually differentiated by their viscosity, temperature resistance and additive packs.
  • This usually classifies waxes into three groups based on intended usage:
    1. Cavity wax;
       • Used in cavities, holes and crevices.
       • They usually have low viscosity, low resistance to abrasion and chemicals and low temperature resistance.
       • These "disadvantages" provide them with very good flow and "creep" properties (they seep and flow into pores, seams, cracks and other tight spaces and embed themselves to seal them).
    2. High temperature resistant wax;
       • Used in the hot engine compartment, or on the underbody and in wheel arches.
    3. Underbody wax;
       • Usually have higher resistance to chemicals (salt, urine, crap, acidic mud, etc.) and somewhat higher dry film thickness and some self-sealing / self-healing properties (if scratched or chipped, the coating re-seals the gap on itself).
• There are also some "hybrid" products which are a mix of wax and bitumen, or wax and oil, etc.
  • Such products are an attempt to combine the best of two worlds.
  • Example 1: Car System KS-800
  • Example 2: Hammerite Waxoyl

Advantages:

• Very good creep-in and sealing properties inside cavities, crevices and holes.
• Usually somewhat transparent, enabling to see what is underneath them.
• Usually have some self-sealing ability when lightly damaged (scratched) by rock impacts or minor scuffs.
• Relatively easy to remove by applying degreasing products.
• Dielectric, so safe to use on wiring and electrics.

Disadvantages:

• Usually have to be applied by a forced air gun or from a compressed air spray bottle ("rattle can");
• Can be a bit toxic to the operator during application (not after they dry);
• Can be relatively expensive depending on the product;
• Wash off and scrape off relatively easily, requiring regular check-ups and re-application on such areas;
• Product quality can vary highly depending on the manufacturer;

Conclusion:

• Waxes are an excellent choice for application inside cavities like inside the doors, sills and chassis.
• Relatively poor abrasion and washing off resistance is the main disadvantage of waxes when applied to the underbody, especially for all-terrain driving, where direct contact of the underbody with mud, snow, grass, branches or rocks is expected, as well as regular thorough power washing of the underbody.
• Regarding the underbody, a wax might be the optimal choice only for the parts of the underbody which are somewhat obscured from direct contact with the ground (deep mud, deep snow, etc.), like above the fuel tank, above the gear box, etc.
• A high temperature resistant wax is a great choice for the engine compartment, unless the car is going to wade through deep muddy water or through mud holes.

Lanolin

• Lanolin, also called wool wax, is a natural product from sheep.
• It has a very long history of wide array of uses, one of which is protection against rust.
• Lanolin-based vehicle underbody rust protection products are yet another compelling choice.

Advantages:

• Hermetically seals the surface.
• Relatively good wash-off resistance when power washing is applied.
• Some lanolin-based anti seize grease is alleged to last 10 years on bolts in sea water.
• Usually ecological and harmless to health during application.
  • Note: While lanolin itself is completely harmless and even eatable ("food grade safe"), any additives in a lanolin-based product might not be!
• Relatively easy to apply - brush on or spray bottle or compressor.
  • Easy to clean off if it gets where it should not be, including hair and eyes.
• Should dry to a semi-hard waxy resin (product dependent).
• Dielectric, so safe to use on wiring and electrics.

Disadvantages:

• Most lanolin-based products smell like ... sheep.
• Abrasion resistance insufficient for hard-impact areas, like inside wheel arches.
• Product quality can vary highly depending on the manufacturer;

Conclusion:

• With a proven several thousand year old history of use as (salt) water repellent and a few decades of history as a vehicle underbody rust protection product, lanolin is a compelling choice.
• Just like there are different types of wax based products for different areas of the vehicle, so are different lanolin-based products.
• Lanolin could be viewed just as another type of wax, which would even be roughly correct, so similar conclusions for the waxes are valid for the lanolin as well.

Oil

To be written...

Synthetic resins

To be written...

Polyurethane

To be written...

Typical examples of such coatings are U-pol Gravitex and U-pol Raptor.

Popular application combinations

Many people who restore old timer vehicles take the following procedure:

1. Wash the underbody and the cavities.
2. Completely dismantle the vehicle.
3. Cut out any rotten parts of the cabin and the chassis and patch weld them.
4. Sand blast the chassis (if it exists), the entire cabin and most suspension parts.
5. Spray the the entire cabin (except its underside) with 2K "normal build" epoxy primer in two coats (with the application of a polyurethane seam sealant in between to most panel joints and all welds).
6. Spray the entire cabin (except its underside) by a top coat.
7. Spray or brush the underside of the cabin with a 2K "high build" epoxy primer in two coats (with the application of a polyurethane seam sealant in between to most panel joints and all welds).
8. Spray or brush the underside of the cabin with an underbody wax.
9. Spray the cavities in the cabin with a cavity wax.
10. Some people take the sand blasted chassis, suspension arms, axles and other "thick metal" to be hot dip zinc plated.
11. After zinc plating, they spray or brush zinc plated parts with underbody wax, including cavity wax for the insides of the chassis.
12. If no zinc plating has been performed:
    1. They spray or brush the chassis and suspension parts with two layers of 2K "high build" epoxy primer paint (with the application of a polyurethane seam sealant in between to all welds).
    2. They spray them with underbody wax, including cavity wax for the insides of the chassis.

• The described method provides more than enough decades-long underbody rust protection for on-road old timer vehicles.
• Either the zinc plating or the epoxy paint will easily withstand all usage scenarios through which such vehicles will go through during the next decades to come, especially with wax on top of them.
• However, these layers of protection are not enough for all-terrain vehicles which are used in all-terrain duty.
• An additional anti-stone chip layer is required between the epoxy paint and the wax on all sections of the underbody and suspension parts which have relatively high risk of abrasion.

Final notes

• Heat up the wax prior to application by putting the bottle in hot water for a while.
  • This will significantly improve the flow of the wax and its spatial placement.
• Use proper protection for eyes, ears (if using power tools), hands and your respiratory system!
• Observe the manufacturers' application guidelines for each used product!
  • This refers to surface preparation, shaking / stirring / mixing before use, application temperatures, methods of application, drying times, expiry dates, etc.
• Check occasionally (at least once a year) for any underbody damages, cracks or delamination of coating.
  • Re-treat the problem area as soon as it is discovered.

• Entrusting an underbody rust protection job to someone else (even to specialists) is generally risky, as the usual time constraints of handymen and professional firms can lead to "chuck it on, cover it up and give it back quickly to keep up the schedule" application methods.
  • Therefore, it is very important to discuss with the contractor about all the details of how all the phases of the job will be done (and check up on them a few times during the execution) in order to avoid skimpy execution.
    • Be prepared to pay / "tip" them more for a thorough job execution though!

Products and manufacturers

Top quality manufacturers of various underbody anti-rust protection products (in alphabetical order):

• 3M
• Bilt Hamber
• Car System (Vosschemie)
• Dinitrol
  • Another official web site
• Hammerite
• Mike Sanders
• Valvoline/Tectyl

Manufacturers of cleaning products (traffic film removers etc.):

• Atas
  • Atas' Dimer traffic film remover product

Unsorted quick tips

This chapter contains some new quick tips which were added in a haste and thus there was no time to properly incorporate them into the chapter(s).

1. If performing forced air drying of cleaned and washed surface prior to application of the next layer of coating, make sure that the air compressor has an oil filter installed in its compressed (output) air line. If not, the compressed air might contain small droplets of oil, which will re-contaminate your pristine clean surface during forced air drying.
2. It is highly recommended to use "high build" primer coatings, especially on bare metal.
   • This property refers to their nominal film thickness, but this property also implies some other beneficial and physical characteristics.
     • Read more here.
3. Wire brushing (both manual and powered) tends to actually polish the surface after initial abrasion or the rust.
   • Therefore, the surface has to be abraded after wire brushing and before painting, preferably by lightly sand blasting it, but some vigorous manual sanding with a 150-200 grit sand paper is also better than nothing.
4. If using acids to remove rust (like citric acid, caustic acid, hydrochloric acid, etc.), beware of thre major issues:
   • Most acids have to be neutralized with a base - simple water rinsing may not be enough.
   • There is a high risk of the occurrence of the phenommenon called "hydrogen embrittlement" of the iron or steel surface, which can severely weaken it - important if it is used under stress.
   • Strong acids can significantly "etch" the bare metal.
     • This is great as a surface preparation for applying a primer coat.
     • However, acid etched or sand blasted steel is highly susceptible to rusting (sometimes within minutes), and therefore you have to paint quickly after acid etching or sand blasting.
5. This guide contains some very useful and practical info on DIY application of 2K high build epoxy primers.

Additional reading

These forum topics deal (at least in part) with rust in Jimnys:

1. Project "Rust bucket";

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Page last edited on 22/12/2021 by user Bosanek