View Full Version : Powder Coat or POR15 Frame?

05-19-2005, 06:32 PM
O.K., I've researched all the archives here and other TR forums and I need to make a decision with respect to what finish to use on my Frame. I'm just about done stripping it all down.

Until last week, my mind was made up to Powder Coat it but the Body Shop that is painting my Tub has quit using the process for frames and suspension parts and is exclusively using POR15. While in his shop, he took me over to a frame from a project he is redoing due to an accident that was Powder Coated almost four years ago and rarely driven. He hit it with a hammer (lightly) and the finish cracked and a nice chip flaked off. Next, it was on to an a-arm from the same car that was POR15'd at the same time and wacked it very hard, no noticeable change in the finish. He claimed that for years he had been Powder Coating Frames because it was easy to send out and fairly cheap but swore by the POR15 for the small parts he could bead blast in his small cabinet.

After the example, I have been bringing all my small bits to my office, bead blasting and POR15'ing them, the finished product is pretty spectacular. I have a Powder Coater lined up to take my frame next week but am having serious doubts. Does anyone out there have any long term experience with the Powder Coating and its related durability? Everything I read about the Powder Coating process sure is convincing that this is the right approach but seing the example first hand by my body guy has me questioning my decision.

Any help would be greatly appreciated.

Dave DeWalt

05-19-2005, 07:38 PM
Hi Dave,

Not too long ago I went through the same questioning process as you, deciding how to re-finish my TR4's frame. I've now got a POR15-coated frame in my garage. It was stripped to bare metal (mostly sandblasted), repaired as necessary, prepped and gray POR15 applied. Over that a finish coat of Chassis Black was applied. All was done with cheap throwaway brushes and foam pads. The results are fine for a frame, probably look very much as it looked new from the factory. (I still will be injecting Waxoyl or similar inside the frame rails, since that's where rust starts and eventually destroys the frame.)

One problem with POR15 is that it will discolor from exposure to UV light. I've seen this on some other parts and it starts looking yellowish after a year or so. The more exposure, the more it will discolor.

I used silver POR15 inside some motorcycle fenders and that showed UV discoloration pretty quickly. The paint still seems sound, though. Hence the top coat of Chassis Black on my car's frame. This is UV safe, but nowhere near as durable as the POR15 base coat it covers.

If I were doing it over, I might use flat black POR15 first, then the semi-glossier Chassis Black over it. That way any chips in the top coat wouldn't be as obvious. Using gray under black made it easier to see anything missed with the top coat, though.

Personally, I'd hate to apply POR15 with a spray gun. It uses very strong solvents and needs prompt attention to cleaning up afterward or a gun will be quickly ruined. If your body shop is doing the job, fine. If not, well it's up to you.

I think properly applied powder coating is nearly as durable. And, it "flows" to nicely cover any flaws and makes for a very nice finish. (POR15 flows well too, actually shows very few brush marks.) Yes, powder coat can get dull with age and eventually might flake, especially if water get under it and some rust starts. Powder coat is difficult to touch up if that's ever needed. Really the whole job needs to be redone at one time, to do it right. Due to the electrically charged nature of powdercoating, it can be difficult to get it into nooks and crannies, which is often the most critical place on a frame to get good coverage.

If I had the equipment for powder coating, I'd try it on small parts especially.

On chassis parts, many racers specifically avoid powder coating and will only use a fairly thin coat of paint. They do this because stress cracks and damage can hide under powder coating or heavy paint. They want to be able to visually inspect the chassis and address small issues before they cause something more catastrophic.

Both powder coat and POR15 would be buggers to remove, if you ever have a change of mind!

It can be difficult to paint over POR15. It's very tough to sand and many paints don't stick to it well (their own Chassis Black is fine). They do offer a Tie-Coat primer for use on top of POR15, prior to applying another type of paint on top. I've not tried that.

POR15 holds up better than most paints close to the heat of welding. I plan to coat the inside of some rocker panels with it, before installation (not directly on the areas to be welded, though).

I hope this helps you with your decision.



05-19-2005, 08:37 PM
One other option that I had never heard about until I purchased my 2500M is a finish POR15 makes called Hardnose Paints (https://www.por15.com/product.asp?productid=249). My frame was POR15'd for rust protection then covered in Hardnose Blue. Beautiful color and very tough. I'd do it again if he hadn't done it (though I would have used Dark Blue).

05-20-2005, 03:01 AM
Hi Hayfever,

This Hardnose Paint look interesting! I think I'll try it sometime.



Simon TR4a
05-20-2005, 11:13 AM
Dave and Alan, I was about to ask the same question, my frame is going for sandblasting and motor and tranny mount welding at the end of the month.
I had almost decided on a zinc primer (sacrificial) and Tremclad rust paint, but now am not so sure. This, I felt, would be better than the factory did and I assume modern acrylic or urethane enamels are better than the ones from 40 years ago.
I don't feel uv rays will be a big issue under the car, so if POR15 is really superior I may just use the other stuff for suspension bits, gas tank etc.

05-20-2005, 12:08 PM
I too am in the midst of a frame-off and trying to decide on coatings. There is another product, Eastwood's rust encapsulator, which has not been mentioned. I have no experience with this product but they claim to be superior to POR 15 see write-up at the link below. On the flip-side I'm not so sure this isn't just overkill. After pulling my body and inspecting the frame I had only superficial surface rust after 30+ years with zero coatings on the frame but for dripping oil and some oversprayed Ziebart. I'm of the opinion that you can't really prevent rust, just slow its growth by coating and providing escape and evaporative routes for any trapped moisture.


05-20-2005, 01:19 PM
Why the issue with UV sensitivity?


05-20-2005, 06:58 PM
The "chassis coat" offered by POR is a great "top-coat" to be applied over their original POR15 product. It will prevent the UV deterioration of that product. However, the "chassis coat" all by itself does not have the hardness characteristics nor the rust encapsulation/chemical reaction thus not nearly as durable of a finish.

I'm really not so sure I need to worry about the UV fading for the frame since the sun really isn't going to reach that point. But, my body guy still suggests it or their new "hardnose" top coat as mentioned above as it will add to the overall chip resistance of the undercarriage and susp. bits.

My car will not be a trailer queen and will be driven almost daily on my short commute to work. I want a finish that will truly last over the long haul. "Pretty" is nice but I want the most durable stuff I can put on. I have no intentions of pulling the body off ever again.

I still haven't heard from anyone that has actually had long term experience with their "Powder Coated" frame. Anybody want to chime in on how it's holding up?



05-20-2005, 10:01 PM
I am doing a frame off on my GT6. I used the rust encapsulator, then covered that with Eastwood chassis black.
You can get both in spray can and by the pint and gallon.
It is VERY easy to work with and turns out looking pretty good.
I highly recommend it.
Of course I stripped the frame first.

05-22-2005, 10:01 AM
We're almost at this stage with the MGTC....still unsure of what we're going to use but it will porbably be POR15...Powder coated many small parts and they turned out great, but since it's still in restoration no word on durability. I remeber reading somewhere that powder coating frames can make the holes in it smaller thus making it very difficult to reassemble just another factor to consider...

05-22-2005, 12:11 PM
I have used all of the above mentioned products and processes and offer the following observations:

POR-15 is great, but preparation is the key to success. It is meant (and truly requires) a rough surface for good adhesion. DO NOT apply this to a sound, smooth, metal piece and expect the results you saw when the guy struck the POR-15 coated trailing arm. It is essential that the metal parts be rough. Sandblasting with coarse media is OK but just like with the rusted steel, it must receive the phosphoric acid treatment (Metal Ready product or similar). Secondly, the application of two coats is also mandatory. This is tricky as the timing of the second coat application must be correct. You must wait until the first coat is just slightly tacky before applying the second coat. Too soon and you'll get pin holes through the second coat as solvent comes off the first coat... too late and the second coat won't adhere to the first coat. As for their Tie-Coat primer for POR-15 paints... it is not worth the money. The trick is to apply a coat of your own top coat compatible primer as a fog coat when the second POR coat is just slightly tacky. Then heavily prime over the POR a day or two later.

Hardnose paints are NOT the same as the POR-15 paint. Hardnose paints are indeed designed to be chip resistant but they are NOT designed for corrosion protection. They are great to apply over a regular POR-15 base coat. (My milling machine is coated with Hardnose grey).

As for spraying POR, the comments about ruining a good gun are true. I have limited my spraying to small areas (no larger than a few square feet) which I apply using a CHEAP Badger air brush. These can be cleaned with regular lacquer thinner but must be cleaned as soon as possible or you'll just throw them out. You could also buy small panel guns from sources like Harbor Freight and throw them out when they become gummed up. Don't use a good gun with POR.

In a former job we used to routinely powerder coat industrial equipment. I took in several automitive parts to have them powder coated. The coatings are wonderfully smooth but as mentioned they are brittle. As with POR, surface preparation is key to good results. Better results are had if the coating is thin and the surface sand blasted (and completely rinsed to remove dust). I would not use powder coating on items that can be struck by stones. However, contradictory as this sounds, I've seen wheels very nicely done with powder coat.

The Eastwood products are excellent and very easy to apply. Rust Encapsulator used to be called Corroless Paint (forgive the spelling). It is a thick, chemically active primer that applies like "regular" paint. I don't think it sands particularly well but otherwise is OK. I LOVE Eastwood's chassis black paint and I always keep it around for projects. I apply it as my top coat over POR-15 paint to protect it from UV exposure. The only caveat is you DON'T want to apply more than two coats of Satin Chassis Black as the gloss gets higher and higher with each subsequent coat.

05-22-2005, 12:56 PM
Clean (sand/grind/sandblast), repair, prep (Oxysolve) frame. Paint with good 2 part epoxy primer (I like PPG's DP-40). Then give it 2 coats of polyurethane in the color of your choice <g>. Add a dulling agent if you desire.
(Mind the respiratory protection requirements for isocyanates).

Powder coating is both expensive and over-hyped.

POR is difficult to work (see above) and won't stick to your frame if you're prepared it the way it really needs to be prepared anyhow (for longevity).

I've pretty much sanded off everything I painted with Eastwood's old 'Corroless' over the years (what didn't *fall* off...).