painting over por 15?

[scott]

bulkhead has 3 coats of por 15. it's been curing about a week. about to put the color on, dupont centari acrylic enamal. what if anything do i need to do to the bulkhead before i begin spraying?

[greenmeanie]

Look at POR15 website. I think you need to use their special primer to get anything to adhere to the POR15 itself.

Make sure you top coat all the POR15 as it is UV sensitive and will lose its useful properties if left uncoated. They sell chassis black top coat for the purpose. My one complaint about POR15 is that you have 2 pretreatments plus 2 coats of POR15 and 2 coats of chassis black to achieve the same protection that other paints achieve in a single coat. It is good but it is not cheap and it is a bit of a skiddle.

[thixon]

Scott,

adding to what Gregor had to say, I've got some advice on Centari. It's been a while since I shot it, but I seem to remember it being a little thick, and laying down a little funny at first until I got my rythm down. If I remember right, I abandoned trying to adjust my gun, and ended up backing my needle out all the way. I then just varied trigger pressure to control how much paint I layed down.

Also, that stuff has iso's. What are you using for a respirator?

T

[scott]

for resperator i'm shoving old brake lines up my nostrils, sealing 'em with a bit of duct tabe and running them out of the paint tent. but as a back up i've got the $30 3m disposible that is suppose to good for about 15 hrs or whatever. i jus remember it was a lot longer than i was planning on spending painting.

when you sprayed your centari did you use a reducer. my can says 8-1-4. you sound like a painter and i don't mean to offended

[thixon]

No offense taken. I'm not a pro, but have painted my fair share of cars.

I did use reducer, and followed the directions accordingly for mixing. I used a satajet, and again opened the needle all the way. If your gun works like mine, you can control the amount of paint coming out of the gun by how far back you pull the trigger. I ran it at the recommended air pressure, and don't think I cranked it up further. Overall I was pleased with the results.

The only thing I'll say about the respirator is that the 3m job won't protect you from exposure to isocyanates. That said, I'd be lying to you if I said I'd never painted a car using the mask you've got, and done so using paint with hardener containing iso's. Just be careful, read up on the effects, and decide for yourself. A hobbyair set up can be had for $600 or so. Heck, you might be able to rent one locally?

[thixon]

Scott,

I just checked prices on a hobby air. Looks like prices have come down since I bought mine. Looks like you can get the half mask version for under 400 bucks.

[luckyjoe]

You can easily top-coat POR-15, but you have to spray prime it while "still tacky". Once the POR-15 has dried/cured, you have to use their special primer/procedure...

Regards,

[scott]

my disposible was recommended by the guys at the auto paint store were i got my paint. a repretible org that knew what they were selling me in the way of paint. these guys supply a lot of the body shops around here.

my gun is hvlp gravity fed and i am fairly happy with the way the por15 laid down and i didn't thin it at all and it was my 1st paint job. now i get to practice some more by put'n down a coat of self etching primer befor i spay on the limestone. all this spraying is to build the skills i need to make my spitfire look nice. PD (what i call my series) is going to look like some experiemental subject mutant when this is done but she'll not die of rust

[DADAMS]

Hi, I'm newly registered, but I thought I would share my recent experience with painting over POR15. I'm not new to spraying and am a stickler for following instructions because I spray a wide variety of different products (wood finishing for custom millwork). I even spoke to the tech service at POR15. I had 2 coats of gray POR15 on a mess of parts, axle casings, brake drums, swivel housings and so on... I ended up with adhesion problems between the cured (2 to 4 days) POR15 and their TieCoat primer...

The thing I skimped on was not scuffing the cured POR15 with coarse enough grit to give it some tooth for the tie coat to bite onto. I ended up with a weak bond that I could scratch off the tie coat with my thumbnail. It was very discouraging.

I would caution to scuff the POR15 heavily and thouroughly to promote adhesion. I had used a combination of green ScotchBrite and 320grit sponges. I had thouroughly dulled the surfaces, but apparently not enough to get proper adhesion.

It may be too late, but your best bet is for a chemical bond where you lightly prime over a tacky POR15 final coat. All your coats of POR15 should be on slightly soft previous coats. I forget their terminology, but its something like 'finger drag dry' or like that... it means that the paint is just dry enough that it doesn't come off on your finger when you touch it... that time can vary a lot. I painted in April when humidity was fairly low with indoor temps around 65. I needed to wait appx 4 hours before the paint could be touched.

I hope this helps. I ended up with a lot of rework to get back to where I was. If you're painting on fully dry POR15 base coat, break it back with coarser grit. If you burn through to the metal, shoot it again with POR15 and follow their directions for priming onto the tacky surface...

Its good paint. I've used it a number of times before, this is the first time I've had trouble with it.

Good Luck and take your time

[scott]

so my only option is mechanical? there isn't a self etching primer i can spray over the one week dried por15? dang it's going to suck trying to scuff up all the nooks and cranies of a bulk head.

[Jim-ME]

Scott,
POR-15 sells a gray etch primer. I have not had problems using their primer.
Jim

[thixon]

Scott,

A possible option is an epoxy primer. That stuff sticks to everything, including bare aluminum. In fact, most auto paint shops will recommend an epoxy primer instead of an etch primer. Call POR 15 and see if it'll work. You can source it at your local auto paint store. Dupont makes one under the Nason brand name thats not expensive and works great.

Just a thought.

[scott]

thanks dudes! i've been to por's web site and they say to sand cured por15 before hitting it with their self etching primer. i call 'em and ask about epoxy primer

[scott]

por-15 guy said to scratch it up with a scotch scratch pad, about a 320 grit. self-ectching primer next would help but ain't neccessary. he says you just need to get the shine off it. now remember this is for por-15 that has cured for over a week. if you care i'll let you know how it goes next week