Underbody Prep & Preservation Discussion

if anyone wants to do this to your floors my advise would be to prep the floors 1st. i would grind down the rust clean the flrs then use por15 ready prep then wash thenm down dry and next day paint. the painting part uses alot of time. alot more than i thought and make sure to have gloves and a long sleave shirt. my one arm has paint all over it and it will not come off. i usually think gloss black makes thing look worse unless it is perfect so i used semi gloss but when it was wet it looked better than when it dried. also i was planning on either udercoating or using a bedliner coating so it does not matter alot on the color. i put 1st coat on took about 2.5 hrs the can says wait 2 to 6 hrs for 2nd coat and have a slight drag to the touch on the coating. when i did the 2nd coat it was raining out and now the paint looks alittle blotchy. the color looks a little uneven. i dont know if it was the humidity . it will not matter once i top coat it with a under coating. i got home around 2:45 and then had to be back at shop at 8:00 to get car off the lift so my buddy could work luckily it was dry. hope this helps anyone planning doing there floors

Please keep a very close eye on that body. Any place where POR15 gets punctured or scraped, it will start to rust underneath, and you won't notice it until a whole large patch comes off in a few years. I no longer use POR15 on anything that has any remote chance of seeing an impact or a puncture (which is just about everything).

^ What do you recommend?

1. Clean (degrease, scrape, wirebrush)
   
2. Acid wash or other chemical rust remover (I have had adhesion failures by not doing this step)
   
3. Lay down a good primer like a zinc-enriched primer
   
4. Topcoat, use a rubberized undercoating if you like, I have had decent success with this on inner fenders where you get a lot of rock and gravel projectiles.
   
5. Spray with clean used motor oil or an undercoating oil, then drive down a dusty road to build up a dirt cake on the undercarriage. If you like your mechanic, do this immediately AFTER the annual inspection.
   
6. Re-cover any new rust spots annually, like in July, so you can let the paint cure a bit, then re-oil it.

And let me be clear - I'm not knocking John's work, and I know for a fact that I struggle with really getting the surface cleaned and prepped good enough. My 9C1's undercarriage looks pretty good, but every other car I did with POR15 (and I did several), the POR15 did not survive but got undermined, and it's a tough job to remove and re-prep. I should take some pictures of my '94 wagon on the lift right now so you can see what I'm talking about.

Standard paint immediately blisters when it's got problems underneath so you immediately know what you need to fix. POR15 does not.

One other thought - in areas near exhaust, there is benefit to doing a light colored paint as it's more reflective of heat than black. John, again, keep moving forward, you've done a good job, and if your prep is better than better than mine (which it almost certainly is), you're much better off.

Here's an interesting read for anyone who cares. These folks sound smarter than me.

various paint options.

On second thought - moderators, could you delete my posts or move them to another thread? This is John's thread and I don't want to threadjack it.

no problems with your statement joel. i do plan on either a under coat or using a bedliner coating. i would never coat it with oil that would drive me crazy. my wagon is used alot less than most, it gets put away every winter

I've thought about the bedliner idea... the oil would drive me batty too. :s

No inspection here, so it would only irritate ME.

Hahaha.

we have inspections here but under 5k a year you get a exemption sticker

To the moderator who made this thread - thank you!

Let me be clear - those of us in the humid northeast have a completely different corrosion situation than folks in other parts of the country. It is an ongoing battle to keep metal as metal. If you can avoid moisture contact, condensation, and whatever else may contribute to the oxidation of your metal, you don't even hardly need to paint.

When I first got my '94 wagon from Miami, FL, I removed the entire exhaust system with hand tools. The underside was amazingly rust-free. But it had rust in the rain channels along the top of the doors. So there's different situations for each area. If I lived in FL, I would probably just clean and paint the underside of my car with regular paint, blow some rubberized undercoating on the areas that would see gravel and rocks, and be done with it.

For my area, we got a lot of rain and winters basically have the cars going through a combination of salt water and freeze/thaw cycles. Edge rust is really what starts to do a car in up here - John, pay close attention to edges when you reassemble the car, and anywhere where a bolt is going to chew into metal, put some never-seize or grease on it to protect any paint damage. If you ever watched that reality show with Boyd Coddington, whenever they assembled a car, they used painter's tape on any surface that might get scratched or abraded during assembly to prevent paint nicks. When I put my inner fenders back on after getting them powdercoated (and then I sprayed undercoating on top of that), I used painter's tape on every edge to protect them while I reinstalled them in the car. Every protected edge has made it through several winters with no rust. I also use oil because of its creeping properties - it will spread out and coat edges, but you do have to reapply it every year.

Also, as far as paint coatings go, I'm sure there's good stuff out there, and if i had the talent and facilities for good prep, my experiences with POR15 would be better. It IS holding up very nicely on my 9C1 which I drove through this winter. But more than any other coating, regular paint, if it gets compromised, will show quickly and is the easiest to remove and reapply.

Joel I agree with you, I used POR 15 once on some inneer fenders that were sandblasted down and prepped as per the directions, well a few yeas later the inner fenders started rusting even on the top side. I never used the stuff again.

I am a firm believer in epoxy prime and U-Phol underocating. Special gun needed to apply thestuff though so not for everyone.

Some local guys here have used SEM rust shield. I only did some under car stuff once. I only did the rear portion of the car because I got lazy. I wire brushed it and used spray cans of rustoleum. After 1 winter, you could see the paint flaking and surface rust creeping back through.

Before





After..





It looked nice. Like Joel said, in Florida, this would be sufficient. But up north, it only lasted a few months before it started looking like the before shots of the floor. The black held up. Maybe additional coats would've helped.

SEM rust shield, hands down. When used with the hardener. Two coats is more than enough to keep the car rust free. I've seen first hand a New Hampshire car that's been treated with it and it's looks minty fresh. I did my floor pans with it last summer and have had zero issue. I wouldn't use Por as the results don't come close to SEM.

rhino liner everywhere ftw,..
almost bulletproof.

Nick

phantom 309 wrote:

rhino liner everywhere ftw,..
almost bulletproof.

Nick

I've seen that work with great success, too. Lots of Jeep and 4x4 guys here do that.