I POR 15'd my Henry J frame couple years ago, did all the recommended prep, put on 2 coats and it laid out smooth. I moved a couple brackets the other day, ground the welds, smoothed it out, wiped the top off with lacquer thinner and put on a new light coat of POR 15. It looked good, next day it turned rough as sandpaper, instructions say it's compatible with all top coats even lacquer based ones, so I would assume the lacquer thinner was ok to use. I ordered their POR 15 primer which is supposed to be their "tie" it all together and make any paint adhere super mojo paint. I plan to smooth it down and give it a coat of this stuff then paint it with another brand topcoat. Just curious if anyone else has seen a reaction like this ?
I've had POR 15 lift when used over really old (Nitro-C) lacquer...but I've also cleaned a ton of parts with lacquer thinner and used POR 15 (with in no primer) with no problem. I think the problem must be the primer you used.
Here's the part where it says about the lacquer based paint, I had the garage temp at 54 but I wouldn't think that's to cold to make it have that reaction.
POR-15 is a moisture cure urethane. While the reaction that causes the curing to kick off is different than with 2 component urethanes, the net result is much the same with both in that the cured product is highly resistant to attack by solvents. But, and this is the big but, urethanes are real sensitive to problems when applied over any solvent residue. According to the guy who owns Southern Polyurethanes, one of the sure fire ways to have problems with urethane is to use lacquer thinner or mineral spirits or any similar paint thinning solvent as a wipedown prior to application of urethane. He says the only way to be sure the surface is adequately clean is to use either a solvent based or a water based wax and grease remover, and to continue wiping until a white cloth with the product comes off clean. The practice of wiping down with lacquer thinner, enamel reducer, or similar products is a leftover from the days of single component paints where any solvent residue might tend to thin subsequent coatings to some tiny degree, but they didn't interfere with the curing of the paint as there was no chemical reaction type cure to interfere with. I was priming some rust repaired areas with epoxy recently. I noticed the tech sheet on the solvent based w&g remover I was using said to allow the product to dry for a minimum of 15 minutes prior to topcoating even though the surface appeared to be bone dry within a couple minutes. And, the tech sheet for the epoxy cautioned against using any cleaning solvents other than w&g remover, so, even when you use a product made for the purpose, you still have to take extra care to make sure its all gone prior to coating with anything using a chemical reaction for curing.
I just don't want it to happen again, I'm trying to move forward, not going back redoing things over and over again. My plan was to sand it smooth, use plane water to wipe it down (instead of the lacquer thinner) then use that primer I posted above. After that it should be good to go for regular paint topcoat. After reading the instructions for both the wax and grease remover and the metal prep it said to wash the surface with water after use of the product, so water it'll be before that primer.
The wax and grease remover should be used before sanding. Metal Prep is a chemical etching product intended for bare metal and will serve no purpose on a sanded painted surface. I use a product called Prime Wash for removing any contaminants before priming or painting.
I understand the process of painting, but after spending several hours researching the POR 15 it's evident you can't treat it like normal painting, it has it's own inherent issues. It seems you can't use any type of "prep-sol" without a chemical reaction with the POR 15, not even lacquer thinner which should be ok according to the instructions.
And the first page of the tip sheet I wrote for por do not use lacquer thinner to wipe down panels. Lacquer thinner and urethane are incompatible. Us urethane reducer for a solvent wipe ,scuff up the hard Por and apply thin coats . If you have bubbling , reduce with a little bit of thinner so it goes on nicely . Do not use it in humid weather. Black moisture cured urethane applied too heavily will bubble And produce a rough surface. At Master coat I advised them in the last few years I've had them stay away from the black moisture cured and go with the two part AG 111 , it's sunlight stable and goes nicely with a brush. They now sell much more AG 111 than the black MCU. The black MCU it's good for people my age that want to touch up a chassis. The correct way to do a chassis, is two coats of silver MCU and one coat of. color The industrial name for the system is the Three Coat Polyurethane System it is the one of the most anti-corrosive systems in existence for the last 30 years
I wish I had known where to find the Master Coat back when I painted this, I definitely would've used it instead. I had discussed on the Eastwood rip off thread on how I painted my 41's chassis back in 1994 or 1995 with it and it's still holding up fantastic. You can see a section of the frame in this photo. But I need to deal with this issue at the moment with the POR 15, not sure where locally I can pick up a pint of urethane reducer but I'll check around.
Any auto parts store that does paint mixing will have it. All the NAPA stores near me do. As well as any dedicated body shop supply store.
Thank you, that one is getting a few upgrades, bigger blower, bigger carbs, high flow regulator, bigger lines, bigger pump, bigger filter, return line.
Ha ha, I have a tendency to lean that direction with everything I build, kinda get carried away that way. I was hoping to get the engine running in the Henry J within the next couple of weeks but this stupid paint screw up has got me going in reverse here.
99% of lacquer thinners are garbage these days. They are barely any better than gun wash and shouldn't be used for any but that.
Thought I was ready to put that primer on but during the scuffing process it started peeling up instead, so now I'm just sanding all of the new stuff off. Hopefully someone else can learn from this and not make the mistake I made here.
I gotta throw my opinion in here brother, I'm not a fan of por15 for anything other than going over rust. The stuff sucks on everything else. But that's just my opinion.
My search started in 1988, when I was selling a popular rust product. I was at a show and had my displays out as usual, and noticed that the silver had a green tint. A man walked up to my stand, we talked for a moment, and he mentioned to me that this primer I was selling was similar to a primer that Mobay had developed. He claimed the Mobay material had little or no sunlight sensitivity and it would do an incredible 8000 hours salt spray. He was the owner of a paint factory in New York State and he attempted this formulation, but on the way home the can burst in the trunk of his car. After that, understandably, he shied away from it. I started asking a lot of questions, but he advised me just call Mobay chemical’s tech department with my questions. You can bet Monday morning I was on the phone with Mobay, where I spoke to an elderly gentleman. Every time I mentioned the black he got a little huffy—his exact words to me were, “It’s silver, like it or lump it.” I asked him where I could get a can of this silver and he told me to call Steelcoat in St. Louis, which I did, and they sent me a bunch of samples. The first thing I did was paint the front of the 38 Packard. It was stripped down to bare metal, and there was pitting on the top where the hood ornament went. Directions were to spray two coats, and I did exactly that. On the second coat the pitting disappeared...I couldn't believe it! Needless to say, I was happy as a little boy on Christmas. So that’s how I discovered a way to level pitting without having to use Nitro stain—and this is when our tag line “Get rid of the Pits” was born. In addition to that, we had an airtight seal so the rust couldn't come back, AND we could use any kind of paint over it. The reason for this is it’s completely solvent proof when it dries. So in my first experiment I discovered that it worked well on clean, steel, it sealed the rust airtight, didn't turn green in the sun, and dried nice and toothy for paint to adhere to it. I started doing all kinds of experiments with body fillers and glazing putties, and have had great success for many years with these techniques. Clear moisture cure urethane is for sealing concrete floors. The clear urethane breathes , when you add a black pigment it's still breathing. If it breathes it will oxidize And when that happens it will peel off in sheets because it's usually rusting beneath it. I wish I had a dollar for every frame out there that was painted with concrete floor sealer with black pigment. When you see all these companies that copied this line they are always are in somebody else's shop painting a frame. This is because most of them do not restore cars and have to rely on the customers that use their products to educate them .I think it's supposed to be the other way around. Oh that felt so good. Share this content FACEBOOK TWITTER GOOGLE+ LINKEDIN
This has been one of the most educational threads for me in a while. I'm one of those older dudes who has used lacquer thinner to wipe stuff down to primer or paint it for way too many years. Thanks.
Most body shops did that for years. Wiping panels down with lacquer thinner and later reducer. The first couple of cars I painted were lacquer and after one screw up I learned the importance of metal prep which made me a strong believer. I wonder how much it would cost today to bring in a 1940's car that's inside out and put 14 coats of black lacquer. You could probably buy a condo.
I stopped using the chassis saver/por 10 yrs ago, Used to swear by it... But saw job's done year's prior looking sketchy at best... Back to epoxy an rustoleum satin black # 7777 for me...