Cheap DIY rust-proof undercoating from Harbor Freight

[JohnCondren1933]

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Phone giving me problems, this is just a quick n dirty rust & moisture proofing DIY undercoating I did after watching some YouTube videos on DIY undercoating.

Why do it? Look under your truck with a flashlight at those plastic electrical connectors to your brakes, taillights & rear differential sensors. how soon till they're coated in a layer of salt & start corroding from moisture ingress.

Strong recommendations not to spray rubberized undercoating, it gets nicked by rocks & then when moisture seeps in the nicks, the rubberized coating traps the moisture at the streel.

What's recommended is a lanolin sticky wax spray that migrates as temperature warms, so if it gets nicked by rocks it spreads again.

3 most popular are Fluid Film, Surface Shield Blaster, & Wool something. Base in all of them is lanolin, a sticky wax dissolved in a solvent so it can be sprayed.

Most videos show removing the spare tire, underbody panels, & wheel wells to spray in the hidden surfaces, spoiler I didn't do that yet haven't had time, but never let perfect be the enemy of good enough, so this is how I did it in stages

1) pickup house painting supplies - drop plastic, painter tape, disposable suit, nitrile gloves, shoe covers, safety glasses. You'll want them all.

2) Tape the drop plastic to your garage floor where you'll drive the truck on to spray. It's sticky stuff just keep the dripping gunk out of the house. Leave the supplies in thr garage for when you have time

3) pick up your choice of spraycans. Harbor Frieght has Surface Shield Blaster $8 a can I used 4.5 cans.
Get extra red blow tubes, they seem to like to lauch into the recess of your frame.

Spray cans are just easier to get started fast if you dont already have a coating setup.
If you have an aircompressor pick up a gallon bucket it's faster & cheaper.

Just leave the sprays with the painting coveralls for when you got time. A box of clean rags in the pile too.

4) secret to a good thin coating spray: warm cans. This stuff is like wax it likes to clump. Get a warm tub of water & weigh the can down. Should be mild hot but not enough you can't keep your hand in,
I 1st tried in boiling water & the can bottom bulged out from heat expansion you don't want that, you want the can to be nice & warm even after you agitate it.

5) before warming the can you're suited up. Start spraying the inside channels from the top of the vehicle above wheel wells & work your way down.
I started from back removed the black covers & rubber grommets, stuck the red tube into the holes from top down & sprayed up, sides & a little down, heat will make it migrate down over time.

A work light is great so see where the spray is going, when the lanolin is warm & thin, it's easy to wipe off overspray on the paint with a rag.
Otherwise cold it's gooey you'll need a hairdryer to soften enough to wipe off clean.

If it's cold outside your can gets cold, put it back in the warm tepid water weigh it down until the can is warm again, shake it & back in the warm water till all the stuff feels warm after shaking.

The difference betwen warm & cold spraying is horrible, warm liquid coats a wide area evenly with a thin layer, cold spray comes out as a clump like expanding foam & doesn't spread with fingers too well.


6) If you do nothing else, spray those electrical connectors, especially the backs where the wires go in, when those metal connecting ferrules start corroding from road salt & moisture youre gonna have problems.
& spray all your grounding terminals screwed to the chassis. Lanolin is non-conductice electrical safe you can spray anywhere. All that cloth wrapped cables just spray it keep sealed from moisture.

7) then try to spray the inside of the frame through the holes. I kept losing straws so you have to hold the straw in 1 hand & can the other.

There are undercoating can tops with flexible tubing makes it much easier, I'm ordering some now for Part 2.

8) spray the suspension, springs up into the top of the cups, steering knuckles, control arms, everything.
Except try not to get any on the brake disk but a ton of YouTuber channels with shops said it'll be fine if you get some spray on the disk Just drive around brake to a stop a few times & it'll wear off.

CV axle covers recommended not to spray only because if 2 rubber bellow sides stick together so bellow can't flex it might strain during driving & tear.
Honestly for me better lanolin than road salt, spray lanolin & dump some talcum powder or something on it so a buildup & not sticky.

9) spray over any bolts, inside areas that moisture or mud could settle in a muddy drive, the screws holding your underpanels on. When you get time to take the panels off you won't face rusted stuck nuts on corroded screws.

10) and st some point later I'll take the underpanels off when my tubing comes in.

Here's a link for the curious.
https://www.amazon.com/gp/aw/d/B0CBZ1P8G6?ref=ppx_pt2_mob_b_prod_image

If you don't have alot of time or money, you don't need a lift, just do a little bit when you get time, Don your painter gear & gloves, climb under wirh a headlamp & do a bit more spraying, & bag them back up till next time.

Last thing, undercoating guys don't recommend washing before coating, lanolin seals moisture so if bare spots absord moisture its trapped, a bit of dirt helps the lanolin stick & grab.

One even said it's fine to coat over road salt residue because it's not the salt causing corrosion it's salt attracting moisture which the lanolin with encapsulate.

You touch up spray every other year where you see it scraped off. And after coating you don't wash the underside, you just every other year spray a coat over the dirt & lanolin already there.

I noticed my new mav steering knuckles had the coppery film of iron oxide after just 1 200 mile drive through the rain, so they're all sprayed with lanolin too.

These aren't coated & painted like Porsche 911 suspension components so I guess do it now while new.

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[RideSolo]

Good write-up, nice job. I've been considering doing this on both the Mav and the Escape. Hopefully this summer will have decent enough conditions for the job. The one product you mentioned is Wool Wax. That's actually the one I was considering getting. They've got a starter kit of a sprayer to use with an air compressor and bottles of the Wool Wax for around $150 (last time I checked). I've read about people complaining that it has to be done every year, but I suspect that the every other year you mention is probably adequate for most situations.

 

[Jah.]

Live in Florida . I don't drive on beach or /in ocean water . Have mudflaps to prevent road debris / road sand from hitting painted area . Hood protector for front Hood / fenders protection . Mav always garaged . That is how I rust proof my truck .

 

[peeturd]

Some really good stuff here!
Okay my 2 cents;
I mix one qt urethane with one qt BOILED linseed oil (thin with mineral spirits if needed). Spray on with pressurized spray can (harbor freight $30). I’ve used this concoction since 1970 on all my vehicles - no rust and I live in the Adirondacks, no garage, drive every day on the heavily salted roads. I never “refresh” the undercoating. It does take a few days to “harden” up, although to a low durometer.

removing and replacing the under body panels takes longer than undercoating.

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