Rust Treatment & Undercoating In Depth

Rust is the bane of any vehicle owners existence. Toyota has a reputation as a particularly bad offender when it comes to rusting. There is an endless rabbit hole/discussion of products/methods etc. I'll list the products I used with reasons at the very end. This'll be a fairly in depth shopping list/write up but I'll try and keep it as concise as possible.

Time: 5-20 hours depending on project route.

Cost: $200-$1500 (I fortunately had all the tools. Disposable materials and project cost for doing the "full" project was ~$400).

Effort: For full treatment/undercoating, a lot of elbow grease, repeating steps, and waiting between steps. For just undercoating, definitely doable in a weekend.

Where I'm at, rust treatment/rust proofing and undercoating are not cheap. The only 2 shops around me that advertised these services were $75-$100/hour for rust removal/treatment and north of $1,000 for spraying various undercoating products. Anyone can DIY this project. Depending on how in depth you want to go, what tools you already have, and what products you want to use will drastically affect the time/energy/total cost.

Products/Tools:

Wire brushes set (hand brush and drill brushes): $12.99 Small wire brush (for tight spots): $1.19 Flat head screwdriver: $1.99 Needle scaler: $40 (I didn't need one) Soft Brush: $2.49 1-1/2" angle paint brushes x 2: $1.99 each 1" chip brush: $0.59 Foam brushes: $2.49 Disposable Coveralls (get a couple): $10 each Respirator (get a good one): $40

$38 3M P95 / Organic Vapor Paint Project Reusable Respirator 6311, Large Size , NIOSH-APPROVED, Use For Professional Paint Spraying, Lightweight, Flexible, Thermoplastic Faceseal For Comfort (6311P1-DC)

3M P95 / Organic Vapor Paint Project Reusable Respirator 6311, Large Size , NIOSH-APPROVED, Use For Professional Paint Spraying, Lightweight, Flexible, Thermoplastic Faceseal For Comfort (6311P1-DC) - Papr Safety Respirators - Amazon.com

Flashlight or headlamp: Tons of options, I'll just say $20.

Masking Tape: $8

$8 3M 26334 Crl 3/4" x 55m Automotive Performance Paint 233+ Masking Tape, Green

3M 26334 Crl 3/4" x 55m Automotive Performance Paint 233+ Masking Tape, Green: Amazon.com: Tools & Home Improvement

Plastic painters sheeting: $20

$20 Plastic Sheeting (9' x 400') Long - High Density Painters Plastic Sheeting Roll in Box with Dispense Hole for Easy Paint Plastic Covering

Plastic Sheeting (9' x 400') Long - High Density Painters Plastic Sheeting Roll in Box with Dispense Hole for Easy Paint Plastic Covering - Amazon.com

Jack Stands (one or the other):
3 ton $50 6 ton: Jack (take your pick): ~$200 Air compressor (Only needed if using spray gun instead of spray cans. Bigger is better, I used a 6 gal pancake and 20 gal, details later): $130 Air compressor hose: $15 Inline air pressure regulator: $8 Ramps (I had one set and bought a 2nd set, details later): $60 Impact Wrench (Again take your pick. Any decent impact wrench will do, or even a tire iron/lug wrench, socket wrench etc.): Cost varies so widely not going to go into it. Cheapest option is probably a lug wrench.

Cordless Drill: (Again take your pick. Any decent cordless drill will do. You could also do all the wire brushing by hand): Cost varies so widely not going to go into it.

Torque Wrench (Again take your pick. I inherited some expensive ones but had a cheapo HF one prior that worked fine): $22 Degreaser: $7 gallon

$16 Purple Power (4320P) Industrial Strength Cleaner and Degreaser - 1 Gallon, 128 Fl Oz (Pack of 1)

Amazon.com: Purple Power (4320P) Industrial Strength Cleaner and Degreaser - 1 Gallon, 128 Fl Oz (Pack of 1) : Industrial & Scientific

Rust Kutter: 32 oz $22

$23 Rust Kutter - Stops Rust and Converts Rust Spots to Leave A Primed Surface Ready to Paint, Professional Rust Repair Manufactured in USA – Sprayer Included

Amazon.com: Rust Kutter - Stops Rust and Converts Rust Spots to Leave A Primed Surface Ready to Paint, Professional Rust Repair Manufactured in USA – Sprayer Included : Health & Household

Rust Bullet Industrial (amount to buy depends on how much rust you have, details below) 1 Pint $41:

$41 RUST BULLET Industrial - Metallic Gray - 1 Pint - Rust Preventative Coating for Industrial, Marine, Home and Farm Projects, Chip and UV Resistant, Durable Finish

RUST BULLET Industrial Rust Inhibitor Paint 1 Quart - Industrial Strength Protective Coating - UV Resistant Industrial Paint for Metal - Rust Coating Paint - Rust Encapsulator Paint - Metallic Grey: Automotive Undercoat Paint: Amazon.com: Industrial & Scientific

Rust Bullet Blackshell (their top coat paint, not required but recommend it, details below) 1 pint $41:

$41 RUST BULLET BlackShell - Gloss Black - 1 Pint - Corrosion Preventive Coating, UV Resistant Rust Proofing Paint, Long-Lasting Metal Protection

Amazon.com: RUST BULLET - BlackShell Gloss Black Rust Inhibitor 1 Pint Rust Proofing - Preventive Coating - UV Resistant Rust Proofing Coating - Rust Preventer Coating Paint - Gloss Black : Automotive

Cosmoline RP-342 (I used black version, but would use Clear in retrospect) 1 gallon $90: Cosmoline RP-342 BLACK Military-Grade Rust Preventive BULK | Cosmoline Direct, LLC

WoolWax (again I used black version, but would use Clear in retrospect) 1 gallon $65: Woolwax Auto Undercoating 1 gallon Jug. Straw (clear), Bla (woolwaxusa.com)

Spray Gun (I bought the WoolWax "Pro" gun with attachments) $110: Woolwax "Pro" Undercoating Applicator-wwprogun (woolwaxusa.com)


That's a lot of s**t. If you had to buy every single thing on this list, you'd be well over $1,000 invested. In my area, that'd be about equivalent to paying someone else to do it all. Anyways, from here I'll list the 2 routes you can take. Route 1 is the in depth/full project. Route 2 is the less involved project.



Route 1 Full Project
Cosmoline for Frame and High Spray Areas, WoolWax for Interior Cavities

Step 1) Degrease: Remove tail lights. Remove front fender liners (buy replacement clips on Amazon or save yours). Remove rocker panel rubber plugs. Remove wheels/place front/rear/both end(s) on jack stands. Spray all 4 wheel wells, front fenders, undercarriage, and inside bed with degreaser. Let sit 10 minutes. Rinse thoroughly with hose water. Let totally dry.

Step 2) Remove Rust: Use wire brushes on drill, grinder, needle scaler, hand tools etc. to remove rust. Don't worry about getting to bare metal. Remove anything flaking and give surface rust a good wiring.

Step 3) Rust Treatment: Spray Rust Kutter on any rusty spots. Let dry for 24 hours. Once dry, rinse with hose. Repeat 2, 3, 4, etc. times until sufficient results achieved. Rust will turn black/dark brown and be hard to fingernail scrape. After last treatment/rinse/dry, white film may be present. Use soft brushes to dust off film.

Step 4) Rust Coating: 2 coats of Rust Bullet Industrial, 1 coat of Rust Bullet Blackshell. Stir everything thoroughly before each coat. Using brush/roller/sprayer, apply Coat 1 of Rust Bullet Industrial. Let dry minimum 2-6 hours. Once product is dry to touch and no longer wet/tacky it's ready for next coat. Apply Coat 2 and again wait 2-6 hours to dry to touch. Once Coat 2 is dry, apply next coat. Apply Coat 3/Topcoat/Blackshell. Let everything dry minimum 24 hours (I waited 72 hours) before proceeding. If you go past 12 hours dry time during any step, wait a full 24 hours and then scuff with 150 grit before applying additional coat(s).

Step 5) Cosmoline: Mask off doors/around wheel wells with painters plastic. Use aluminum foil to mask off electrical connectors and rubber components. Using a spray gun at ~20 psi, or spray cans, coat all high spray areas in wheel wells, entire frame, control arms, rear axle/diff, etc. with Cosmoline. Take care to avoid spraying electrical connectors and rubber boots/hoses etc. Let dry 1-2 hours until first coat is dry, then apply second coat.

Step 6) Woolwax: Using spray gun at ~100 psi, or spray cans, coat all interior panels with WoolWax. Heat woolwax or thin with vegetable oil at ratio of 1/3 vegetable oil 2/3 woolwax to make it easier to spray. Use extension wands and 360* tip to get inside rocker panels and all the way inside bed. Spray interior of front fenders. Let dry for 1 hour and apply a second coat.



Route 2 "Half" Project
Woolwax All over

I would go this route if you want a cheaper/faster option, if you don't want to spend a ton of time removing/treating existing rust, or if you don't want to do as much dis/re-assembly.

Step 1) Degrease: Optional; remove tail lights. Optional; remove front fender liners (buy replacement clips on Amazon or save yours).Remove rocker panel rubber plugs. Remove wheels/place front/rear/both end(s) on jack stands. Spray all 4 wheel wells, front fenders, undercarriage, and inside bed with degreaser. Let sit 10 minutes. Rinse thoroughly with hose water. Let totally dry.

Step 2) Woolwax: If you have a lot of rust, if you don't want to monkey with removing/treating rust, or if you don't want to spend as much money or time on this project, you can go straight to spraying WoolWax. WoolWax is safe to spray over existing rust and will drastically slow its progression. WoolWax is lanolin based and will displace water. It does not fully dry and will wash off. Re-apply every 1-2 years as needed. Spray WoolWax all over in the wheel wells, the entire frame, inside the rocker panels, interior of the bed, interior of the front fenders etc. Woolwax is supposed to be safe on rubber. I would try and avoid rubber/electrical components but less risk compared to Cosmoline if it gets on them.



My 2 cents about products/methods etc.

Degreasing:
No matter which route you go, I think this is a necessity. Degreaser is cheap and will drastically improve adhesion of any rust treatment, rust paint/encapsulator, or undercoating product.

Rust Converters:
This is kind of optional. I would do it, but you could certainly skip this step in the interest of time/money. Nearly all rust converters contain phosphoric acid to one degree or another. Phosphoric acid on rust is basic chemistry. Spray it on rust and it converts it to iron phosphate. I tried Rust Kutter as well as the Rustoleum Rust Remover Gel and had better results with the Rust Kutter, hence my recommendation. The only downside is that it's thin like water, but spraying it on multiple times worked well. I know other folks have reported good results with Ospho, Naval Jelly, etc. I didn't want to use something that created it's own coating or layer, like the Rustoluem Rust Reformer spray paint or CorroSeal. This was influenced/confirmed by Repair Geek and Project Farm on Youtube. I ended up using a can of Rustoleum Rust Reformer on a wrought iron railing on my house and it did okay.

After the Rust Kutter is rinsed and dry, it leaves a white film in some spots, and black/dark brown rust in other spots. The white film can easily be dusted off with a dry brush. The rust should now feel hard and if you try scratching it with your fingernail it'll feel pretty solid. I don't know a better way to describe it, but if you scratch some untreated rust vs treated rust you can feel the difference.

Rust Coatings:
I ended up using Rust Bullet for a couple reasons. After watching the Project Farm and Repair Geek videos on Youtube, it was pretty clear one of the top choices was an "MCU" or "Moisture Cure Urethane". The 3 products I was looking at were Master Coat, POR 15, and Rust Bullet. POR 15 was readily available in stores around me. After reading a lot of bad reviews, I decided to pass on it, which left Master Coat and Rust Bullet. Looking at the SDS of all 3 products they looked pretty similar, except the Master Coat and Rust Bullet both have aluminum as a component. As we all know, aluminum can't rust. I would have ordered Master Coat's products, but due to the Repair Geek video, they are apparently always out of stock. I found Rust Bullet discussed on some other forums and it has nearly the same SDS as Master Coat. It was readily available on Amazon. I ordered a quart of the Industrial, and a pint of the Blackshell (topcoat). Their instructions say you don't have to top coat the industrial, but in my experience the Cosmoline seemed to stick better to the top coat than just the industrial in the few spots I missed with top coat. Would definitely recommend Rust Bullet Industrial + Blackshell. Master Coat is the same way, i.e. their basecoat silver paint and black top coat paint.

Undercoating:
I chose to use Cosmoline for high spray areas/frame because it has a long track record of being super good for protecting metal against rust and it doesn't wash off. I've used the CRC Marine Corrosion Inhibitor on my boat trailer and I'd say it works equally as well. I've not tried Waxoxyl but have heard it's equally as good as well. Cosmoline dries to a hard waxy touch and can't chip like other coatings. For cleanup I used mineral spirits and while it takes a little scrubbing, it comes off very easily with a solvent.

I chose to use WoolWax for interior panels etc. for three reasons. The first reason is the "creeping" properties of lanolin based products. Cosmoline basically stays where you spray it, whereas lanolin based products like Fluid Film/WoolWax will slowly spread out over time. The second reason is related to the first reason, in that WoolWax won't clog up pinch welds etc. like Cosmoline potentially could. The only downside to WoolWax is that it washes off, but since I used it on non-spray areas like in the fenders and inside the bed it should last longer. Third reason is that WoolWax is supposed to be thicker than Fluid Film. I've not used Fluid Film but I know plenty of people use it/like it. WoolWax is a little more expensive than Fluid Film but the supposed durability theoretically would offset the cost.

Spraying: Tape off anything you're worried about overspray on put down plastic on your driveway, suit up in your coveralls and respirator, and go to town. If doing the rust conversion or not, I would use the clear version of WoolWax. This ensures that you can monitor the rust year over year. If using a compressor, you can either heat the WoolWax or thin it with vegetable oil to make it easier to spray. My pancake compressor had a hard time spraying it. My dad's 20 gal worked better but the gauges on his compressor are broken so I was at the mercy of the cheap Harbor Freight inline pressure regulator to monitor the PSI. They say to spray it at 90-120. I had best results around the full 120 psi, but it was only ~55* outside. If you're using spray cans, I'd get the 12 pack. The nice thing about WoolWax is you can spray it virtually anywhere without fear of it damaging stuff. Cosmoline you have to be a little more careful since its petroleum based and could potentially damage rubber boots, hoses etc.


Pictures:

After degreasing and Rust Kutter. Note the white film. Can easily dust it off and metal underneath is dark brown/black.


After Rust Bullet Industrial. I didn't get a picture of after the Blackshell, but it looks like black gloss paint.


How I taped off before spraying. In retrospect this was overkill. I also suck at taping.


After 2 coats of Cosmoline. Went a little too thick in some areas and got orange peel but it won't hurt performance.


After 2 coats of WoolWax inside the bed.


Overall I'm happy with the results. Since I already had most of the tools, I saved a lot of $$ compared to paying a shop to do it. I know in some areas people have shops that offer FluidFilm/Wool Wax for fairly cheap. If I had that option I would have maybe gone that route, but I've very happy with how the Cosmoline/WoolWwax combo turned out.

Happy to answer any questions/share additional tips etc.

 

Wow. Impressive write up. I’m sold on Cosmoline. Done my Land Cruiser 60 with it stem to stern. BJ74 next, then the Tundra. So how long to do the whole truck properly for you?

 

So to do the full remove/reinstall stuff, degrease, rust conversion, paint, and undercoating probably took about 20 hours of labor, with a fair amount of time between steps to let stuff dry etc. I’m also not a fast worker, and had to remove/reinstall my wheels a ton of times. If you were just doing the degrease/rust converter/undercoating, or even just degrease/undercoating, or used spray cans, it’d probably take like 8-10 hours and definitely doable in a weekend. Just to spray undercoating takes about 1.5 hours per coat including wheel removal/reinstall. If you have 4 jack stands it’d probably only take an hour or less to spray a coat with all the wheels off. Time per step broke down to roughly:

Remove fender liners, rocker panel plugs, and tail lights: 1-2 hours.

Degrease: 30 mins. 5 mins to spray on, let site 10 mins, 15 mins to rinse.

Dry: 2-4 hours.

Wire wheel/rust removal: 2-3 hours, including time to wire wheel everything and remove/reinstall wheels. Heavily dependent on level of rust present.

Rust Kutter/Converter: 5-10 mins to spray on. 24 hours to dry. Repeated this process 2-3 times.

Dusting off excess white rust converter dust/residue: 1-2 hours including time to remove/reinstall wheels.

Rust Bullet: Total time 4-6 hours depending on number of coats. 2 coats Industrial minimum. 1-2 hours per coat including time to remove/reinstall wheels. 2 coats of the Industrial silver paint, 1 coat of Blackshell top coat.

Cosmoline: 4 hours total. 2 coats at 1-2 hours per coat including time to remove/reinstall wheels. 1 hour dry between coats.

Clean spray gun after Cosmoline:15 minutes. Use mineral spirits or paint thinner to spray through gun until clear and wipe down gun.

Spray WoolWax: 1-2 hours total. 30-60 minutes per coat to hit inside bed, inside rocker panels, and inside any frame holes.

Clean spray gun after Woolwax: 15 minutes. Use mineral spirits or paint thinner to spray through gun until clear and wipe down gun.

Let dry 24 hours.

Reinstall tail lights, front fender liners, rocker panel plugs: 1-2 hours.

Cleanup: 1 hour.

 

I like it, logistics exemplified. I have 6 x 12 Ton jack stands and 2 floor jacks. I've got commercial grade air and
every tool needed. I do like the Cosmoline in Aerosol just as the logistics of living in Canada, it's coming from California.
But these other products are very cool. I'm procrastinating on inner doors and rockers on my 60 which currently owns
the jack stands so while it's up, I guess i better get in there.

 

Oh you'll definitely be good to go then! I'm not sure about the logistics/extra cost of shipping to Canada but I know their website says they ship to Canada and Mexico. I bought a gallon for ~$90 but then you've gotta have a spray gun which was another $100 and a compressor. The gallon comes out to ~$0.70 per ounce, whereas the spray cans are on a sliding scale, more you buy, more you save, they come out to ~$1.00 per ounce if you get the 12 pack. I used the whole gallon on my truck so a 12 pack of cans should definitely do the trick. I actually just ordered a 3 pack of cans to do touch ups and get some of the harder to reach spots. Having the truck up on 4 ramps it's still a PITA to crawl around under keep the sprayer upright, although the extension wand helps a ton. I plan on using the spray cans when it's dark out with a good head lamp to really make sure I got everything.

 

great job!

 

Excellent write up and I applaud your tenacity!

 

exactly what i needed. is there a recommended temp range? truck has been parked for awhile but i may be running out of decent weather. may just spray wool wax for this winter then do the whole kit and kaboodle in the spring.

 

Thoughts on undercoating when you live about 2 miles down a dirt road? The amount of mud on the truck in the spring/fall is kind of crazy. Is it worth it to coat it with something as I'll be washing the mud off all winter/spring/fall? Live in the rust belt so want to do something, but also don't know if it will be worth it.

 

Definitely worth it, even more so. They lay down all kinds of chemical bonding agents on gravel roads to keep dust down
in the summer to help the mud bond within itself to stop potholes in winter. Calcium chloride comes to mind, but who
knows what they use now. Those giant white bags you see in highway yards with Chinese writing on them, not freakin'
idea what's actually in them. That stuff sticks to yours truck and holds it all against the underside. So putting
a decent undercoating spray and protectant makes perfectly good sense.

 

Wow! Incredible job!

What part of the world does your truck live in, if you don’t mind me asking?

 

So as far as the WoolWax goes, I had a wayyyy better time spraying it on a random ~80* day we had than the first round I sprayed in ~55*. The cosmoline should have no problem spraying at any temp as it's essentially water. Both products say you can spray in any temp, and the woolwax says that you can heat it in front of a space heater to make it less viscous. I would probably fill one of the spray bottles for your spray gun and then put it in a larger bottle of warm water or something to heat it up. Spraying WoolWax this fall would definitely give you a winter of protection and it seems like it would wash off fairly easily come springtime if you wanted to do cosmoline or keep doing woolwax.

 

Mud/dirt will definitely stick to the WoolWax and wash off in most areas, but the nice thing about is that since it's lanolin based it never fully dries and continuously creeps into the nooks and crannies that mud/dirt might not reach. Since the woolwax is not terribly expensive, it'd be worth it to do an annual or every other year application. As for the cosmoline, this s**t will not come off without a solvent or extreme abrasive. I've not tested it but it's purported to not come off with a pressure washer. Cosmoline won't wash off but it's a little more expensive of a product and prepping any rusty spots is recommended although it does say you can spray cosmoline over existing rust to stop it from spreading.

 

I'm in the upper midwest where they salt the roads like they're trying to turn all the lakes and rivers from freshwater to salt water lol. Vehicles up here rust/decay at an insane rate compared to other parts of the country I've been in.

 

I can assure you, Cosmoline Does Not wash off!! It’s fully bonding agent paint. It’s quite non existent viscosity so it streams and fills cracks and cranny’s. Just have good ventilation and wear and painters suit and eye protection.

 

Yeah and after spraying be prepared for it to smell/off gas for awhile. It's not terrible, but definitely noticeable as you walk up to your vehicle. I'm sure you can spray it and nooks and crannies with no ill effects, but since it dries hard the only place I was concerned about were the small drainage slits along the rocker panels.

 

I cleaned the drain vents with a stick, you are right about the smell. Worth every sniff! I like it and it’s going on the deck of my riding lawn mower this time I winterize it. I’m curious to see how it seals the inner deck at the end of next year. This will be the ultimate torture test.

 

Picking up a new Platinum tomorrow. Canadian friend recommended oiling. Has it done yearly at Canadian tire for about $100 USD. Temps are the teens here, and I don't have the tools or space to do it myself, so I called a shop he found online.

Guy does oil for $350, says it lasts 1-2 years. Or wax for $1800 (!) done once (unless keeping vehicle a long time -- longevity is a little vague.) Wax includes oil-sprayed enclosed areas.

I live on a private (not treated) dirt road, ocean less than 1/2 mi. Only advice the guy had was, after about 3 oil applications, with the dust of the dirt road, the undercarriage would probably start looking "kinda ratty," but "both work." Said he does his own cars in oil or wax, depending how long he plans to keep them.

After buying the truck, I'd rather not spend $1800. Still, I figure with inflation, the wax price could cost less in the long run. My Canadian friend things both prices are "f&*#g nuts!" I'm checking another shop. Anyone have any thoughts/experience/advice on which whether to do oil, wax, or nothing?

 

Curious, does the dealership offer any sort of undercoating service? Might be worth and ask and see if it's something they offer/their rates. Shops around me start at about $1000 to do Cosmoline or Waxoxyl and go up from there. Fluid film and Woolwax are cheaper but still spendy. No better time to do it than when the vehicle is new, but it might also be something you could skip this winter and at most you should only have some minor surface rust come Spring, at which point you could DIY it with the spray can options available. Fluid Film, Woolwax, and Cosmoline (CRC Marine Corrosion Inhibitor is another good cosmoline based option) all come in spray cans and all say they can be sprayed over light rust. I'd maybe wait until it warms up and go that route.

I'm curious why the price difference is so drastic between $350 for oil and $1800 for wax, and also what products is he using? I've read about plenty of people using used motor oil, which dirt road dust then sticks to and creates even more of a protective layer, and then come spring you wash everything off. As far as labor/materials cost go there's not a drastic difference between Fluidfilm/Woolwax vs Cosmoline. The Woolwax was about $65 a gallon and the Cosmoline was about $90 a gallon, and spraying one vs the other is no different beyond your spray gun settings. Spray cans are a little more expensive but then you don't have the cost of a spray gun, compressor etc. to factor in.

 

Great write up and results. I've been meaning to do this for a while, but I just don't have the patience for this kind of work.

 

find a local shop to spray it with NH oil undercoating. I do my truck yearly since it was new, $220 a year.

 

Great write up and kudos for such a detailed application. I am lazy but still hate rust. I spray mine every year with Fluid Film, no prep other than a quick hose rinse. I use a spray gun with wands to get in the frame rails. I also just go right over the top of the old stuff year after year. It is messy and dirty but works. $40 a gallon and an hour or so to apply. My GX470 lasted for a good 8 years with zero rust in the rust belt before I sold it. There is probably enough build up to last a few more years.

 

I debated going a similar route with woolwax and ultimately sort of did, used woolwax inside the bed panels and frame rails. I'll pull the tail lights this summer and see how it looks/possibly spray in there again and inside the frame if it looks like it's drained off. My dad's got a fairly nice scope I can run inside the frame rails to peek at those well, hoping they look nice and wet lol

 

No worries with the Woolwax, it is very similar to Fluid Film. I used it one year I couldn’t get Fluid Film easily.