Rust protection

From BigJimny Wiki
Jump to navigation Jump to search

Note Icon.pngThe content of any article might be expanded / improved in the future - revisit it sometimes.
Note Icon.pngSeen a mistake? Know something that isn't written? Edit and change this article yourself!
Note Icon.pngImages in the article (if present) can be enlarged by clicking on them.


Introduction

LJ-100x100.jpg


SJ-100x100.jpg


Gen3-100x100.jpg


Gen4-100x100.jpg


  • 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.
  • 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 weak points

LJ-100x100.jpg


SJ-100x100.jpg


Gen3-100x100.jpg


Gen4-100x100.jpg


Areas of all Jimny generations which are most susceptible to rust:

  1. Body / cabin and suspension carriers (mounting points) on the chassis
  2. Various factory welding points on the chassis and on the axles as well
  3. Boot / trunk floor
  4. Below the rear seats
  5. Inner wheel arches
  6. Bodywork behind the side plastic mouldings (claddings)
  7. Bodywork behind front driving lamps


Illustrations of typical rust points

LJ-100x100.jpg


SJ-100x100.jpg


Gen3-100x100.jpg


Gen4-100x100.jpg


Body carriers on the chassis

Gen3-100x100.jpg



Area behind the head lamps

Gen3-100x100.jpg




Front floor sections below side door window moving controls

Gen3-100x100.jpg


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 ...


Rear floor section including boot

Gen3-100x100.jpg




General idea

LJ-100x100.jpg


SJ-100x100.jpg


Gen3-100x100.jpg


Gen4-100x100.jpg


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 based (the oldest and cheapest type);
  • Synthetic rubber / plastic resin based;
  • Waxes;
  • Polyurethanes;
  • 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

LJ-100x100.jpg


SJ-100x100.jpg


Gen3-100x100.jpg


Gen4-100x100.jpg


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), or 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

LJ-100x100.jpg


SJ-100x100.jpg


Gen3-100x100.jpg


Gen4-100x100.jpg


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.
    • These are the areas which usually suffer the most from rust on Jimnys, and these areas can then be properly cleaned and protected.


Note Icon.pngThe wiki article "Fuel tank removal and installation" contains a guide on how to remove the fuel tank.



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 rust treatment (elimination) chemical.
    • Its job is to kill the last tiny thin remains of rust which have stayed in some pores or scratches after the mechanical removal has been performed.
    • The best chemicals for this job are the ones which chemically alter (transform) the rust into another non-ferrous material (making it impotent).
      • These chemicals are much more expensive than ordinary "rust melting / elimination" chemicals.
      • An example manufacturer of these chemicals is Wurth from Germany.
    • A rust treatment chemical usually needs some time (counted in hours) to do its job.
    • Some of these chemicals require grinding them off after they harden off, while others allow further coating applications like it's a bare metal.
    • Note that these 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 treatment chemical has done its work.
    • This way, the sanding will also remove the dried excess layer of the rust treatment chemical.


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 the underbody with soapy water or some other dirt and grease removing chemical, and then thoroughly rinse it with clean water.
    • 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.
    • 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. Clean and degrease the entire underbody with cleaners/degreasers.
  8. Chemically eliminate the last traces of rust on the areas where you mechanically removed rust.
    • Use rust elminating acids or even better rust converter/inhibitor chemicals.
      • Rust converters/inhibitors work on the principle of chemically altering the rust itself, "freezing" it or chemically converting it into another substance.
  9. Apply anti-corrosive primer paint on all bare metal surfaces.
    • It is best to use epoxy anti-corrosive primers.
  10. 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.
  11. Apply seam sealant to all previously rust-treated areas which were welded or where two metal parts/panels join together.
    • It is best to use polyurethane seam sealant.
  12. Apply a stonechip coating of your choice (bitumen-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.
  13. Apply 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.
  14. Apply 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.
  15. After wax spraying is complete and everything else has dried out, return all plugs into position and seal them with raw rubber.
  16. Take a vacation.
    • Preferably in an air spa to clean your lungs of all of the consumed fumes from all these poisons.


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 more for a thorough job execution though!


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.
  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

LJ-100x100.jpg


SJ-100x100.jpg


Gen3-100x100.jpg


Gen4-100x100.jpg


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

  1. Project "Rust bucket";



Page last edited on 25/09/2019 by user Bosanek