Oh look, your Sprinter has rust.
POR-15 is a brand of products with a stellar reputation in automotive circles for stopping rust and corrosion. If applied correctly it's totally bombproof, and the entire line is designed to work easily with each other (so much synergy!). I used it extensively on the inside and outside of my T1N Sprinter before I started my actual conversion with the goal of halting the problems that were already there before they got worse and preventing common problems in the future.
"POR-15 works because it chemically bonds to rusted metal and forms a rock- hard, non-porous coating that won't crack, chip, or peel. It keeps moisture away from metal with a coating that is strengthened by continued exposure to moisture."
POR-15 isn't particularly hard to use, but it can be finicky if you don't take the time to do it correctly, and I had some missteps which caused me to waste money and time redoing work. Avoid my mistakes, use my tips, and be smart about your process, and you'll be successful, no worries!
Note: This is a long section, but I'm trying to save you time, money, and tears. Because I love you and want you to be happy. I also use Amazon Affiliate links to help offset hosting costs for this site.
Por-15 Products Used:
- Cleaner Degreaser (Amazon)
- Metal Prep (Amazon)
- Rust Preventative Coating, silver (Amazon)
- Rust Preventative Coating, gray (Amazon)
- POR Patch (Amazon)
- Epoxy Putty (Amazon)
- Self Etch Primer (Amazon)
- High Build Primer (Amazon)
- Top Coat, gloss white (Amazon)
A Note on Safety
Naturally since POR-15 is super effective it's also pretty nasty stuff to deal with and requires some specialized personal protection equipment (PPE). There's absolutely no part of the uncured product line that I'd want to breath, so use a properly fitting respirator with organic vapor cartridges. Chemical resistant gloves, chemical goggles or face shield, and even a Tyvek suit are all smart choices. Seriously people, breathing in stuff with VOCs in the 300s or getting phosphoric acid based products in your eyes isn't fun, so be smart about this stuff and use the right stuff to keep yourself safe.
As a final note, see my disclaimer, because hey, I'm not a rocket surgeon or even an industrial hygienist (that's my father, I just call him to look at MSDSs).
- Chemical Resistant Gloves (Amazon)
- Chemical Goggles (Amazon)
- Face Shield (Amazon)
- TyVeck Suit (Amazon)
- Respirator w/ Organic Vapor/Acid Gas Cartridges (Amazon)
Order Of Operations
In order to be successful it's important to do the right steps in the right order. Prep work sucks; I hate it so much. But it's the difference of being successful or failing miserably, so suck it up and do it correctly so you don't get to do it again. Here's what I did:
- Wire brush/grind/sand off all the loose paint, rust, and other junk. POR-15 likes bare metal best.
- Vacuum then clean with water.
- Clean again with hot water and Dawn dish detergent. Scrub like hell. Be a champion.
- Rinse again with clean water.
- Use POR-15 Cleaner/Degreaser, being super nitpicky.
- Rinse with clean water and let dry.
- Spray down bare metal with POR-15 Metal Prep, keeping surfaces wet for 30 minutes.
- Rinse with clean water and let dry completely (super important to be bone dry here).
- Use POR Patch if needed.
- Coat with POR-15 Rust Preventative Coating.
- Use POR-15 Epoxy Putty if needed and sand.
- Apply second coat of POR-15 Rust Preventative Coating.
- Re-clean if necessary (no need to etch).
- Apply one coat of POR-15 Self Etching Primer.
- Apply POR-15 High Build Primer if necessary.
- Topcoat with two coats of POR-15 Topcoat, spraypaint, or whatever you're into.
- Weep softly to yourself.
Holy. Wow. Yeah... that's an absolutely absurd list, I get it.
None of it is hard, it's just tedious and there's a lot of it. The trick is to get a bunch of different areas going at once so you can just flip back and forth between different areas and different steps. Good music helps. Once your two coats of Rust Preventive are on and dry rain and such isn't going to bother it, just clean and dry before you go on to the next steps.
POR-15's Metal Prep etches bare metal, helps to neutralize rust, and leaves the surface ready for POR-15 to stick to. I used another chemical resistant spray bottle to apply the Metal Prep, making sure not to dilute it.
As you might have guessed, this stuff is phosphoric acid based, so chemical resistant gloves, a face shield, and a respirator are necessary evils.
Application is easy, just mist the surfaces so that they're damp, and reapply as needed to keep the surface wet for at least 30 minutes. Places that have rust will turn black as the rust is neutralized. You can soak parts in the Metal Prep as well if they're in exceptionally bad shape, I used this technique to help clean up some of the smaller parts of my spare tire carrier. Rinse with clean water and let dry before painting.
Rust Preventative Coating, silver
Now we're getting into the meat and potatoes. Unfortunately, this particular meat and potatoes is harder to swallow than some.
The silver color is designed to add reinforcement to highly pitted areas, and contains two pounds of aluminum flakes per gallon. In theory this was just what I needed for my floor that had rusted under the front mat, as well as the entry steps.
The problems is even after half an hour or so of stirring I still wasn't ever happy with the results; the stuff just never really totally mixed together. There were these odd gray metallic swirls in the paint, and when I applied it to the floor the streaks were very obvious there too. It has to have been the metal flakes that the silver has. Unfortunately it says not to shake on the can, so I assumed a drill mounted stirrer is out as well. I don't know what the solution is if you decide to go this route.
POR-15 is weird stuff, and it actually cures with humidity unlike "normal" coatings. Trying to use it in the super low humidity of New Mexico was one of my largest mistakes, and ended up with me having to redo large sections because I couldn't get it to cure correctly.
I ended up doing most of the work at my parent's house in Indiana, where the humidity in the early summer is absurd, and it worked so so so much better there. In my opinion, 45-80% humidity seems to be the sweet spot. Anything lower and it takes a long while to cure leading to problems, and anything higher means the pot life is just too short to be easily used.
I used cheap disposable brushes for this entire step, figuring that priming later on would hide any sins. A Handy Pail and liners is the only way to go about it, and I pour spouts to avoid contaminating the lid, since literally a single drop of water can screw up the entire can.
Even going really light on the paint, it's still a pretty thick coat. The nice thing is at a certain point in the dryingprocess you can easily go back and feather out mistakes and brush strokes, leaving a really nice, smooth finish. This time frame is totally based on humidity, so go back regularly to clean areas up and don't paint yourself into the corner if you're doing a floor or something similar. Be warned however, since if you go too heavy the paint will actually bubble, and you'll have to sand and do it again. Avoid runs at all cost.
You'll know if your prep work wasn't good because the paint will sort of "slide" off, leaving areas that are uncoated, which is more of a problem on vertical surfaces like walls. Going back and feathering them out is the best way to deal with it, but it's infuriating and many, many times worse with the silver color. I never completely found a solution to it, but humidity and super thorough prep work helped.
I used the recommended two coats, and on high humidity days it was easy to get a second coat on in the same day. You're looking for a bit of finger drag, just a touch of tackiness left and then you're good to recoat. If it has cured for a couple months good luck getting anything to stick to it again, you're going to have to sand off the gloss and use a self etching primer. The finished product is that hard.
tl;dr: Prep like crazy, paint in high humidity, use light coats, avoid runs, and feather out mistakes.
Rust Preventative Coating, gray
I switched to this from the silver initially on a whim, and was furious that I hadn't tried it before. Three minutes of stirring and you're good to go, without any of the weird separation issues or the sliding that the silver had.
Everything else I wrote above applies. Just save yourself money and loads of tears and use this.
Self Etch Primer
This is a primer designed to coat over POR-15 without sanding or other prep besides cleaning, and be topcoated within thirty minutes.
I used a good amount of it, but it's pretty awful stuff to use, though the results are good. This stuff cures with humidity, and is super thick. I'd assume spraying this with a gun would be absolutely impossible. Use a respirator, because the VOCs are insane until it cures and it's self etching, so you probably don't want to breath it in and etch your lungs.
Doing the priming in the high humidity of Indiana was a nightmare; by the time I had poured some into my Handy Pail and cleaned up the rim of the paint can and resealed it, the surface had already skimmed over. Pot life is literally 10 minutes at 70% humidity, and you'll go through brushes like crazy because they dry in a couple of minutes of inaction. It was so thick with high humidity that I ended up using an absurd amount of product which left a very less than smooth finish. I sanded it down later because it was driving me nuts, which left a pretty nice finish. If it's not gonna be visible then I probably wouldn't worry about it.
The worst part was I had about three brush strokes after applying it to get it feathered out before it cured to something like very thick, mostly dry, super tacky latex paint. Seriously, it was not fun.
If you can use, this on a cool day with low humidity. Colorado would be perfect. The Midwest? Not so much.
tl;dr: Dries insanely quickly. Smelly as hell. Use in low humidity. Works well but sucks to use.
High Build Primer
High build primers are designed to build up some material so that you can sand it down nice and pretty before you paint it. This stuff cures like a normal paint, which means you can only get one coat on per 24 hours, so plan ahead. I used it along my door sills and places in the interior that would be visible and I was looking for a nice finished look. It's designed to go over the self etching primer, and I used three coats most places. Use a high quality brush, but you're sanding it all out anyway so no worries.
I hand sanded with 120 grit paper, then took it down to 320, which left a nice, smooth finish. I didn't wet sand at all, which I'm not sure is correct or not. It's a time consuming step, but it's kinda fun to see the finished result. Just take it easy on the sanding and you'll have really nice results.
tl;dr: Three coats with 24 hours in between over self etching primer. Sand to make pretty.
Top Coat, gloss white
This is the final step in the POR-15 universe, and I used it on my floors before I insulated and put down the subflooring as well as the steps and wheel wells. It creates a bomb proof finish, but it takes 3+ days to fully cure, so give it time so you don't ding it all up. I waited over a week before I reinstalled the seat pedestals. It adds thickness, durability, and UV protection, so I figured it was a smart move, plus I'm sure you get some sound reduction as well. Done correctly it chemically bonds with the POR-15.
I didn't read and used self etching primer before I used the topcoat (because I hate myself). Allegedly it's not necessary as long as the POR-15 is about two weeks old or less. It cures with humidity and is on the thick side, but not nearly as bad as a two part epoxy finish. Two coats leaves a nice, pretty finish, and overall it's easy to use.