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I'm in process of putting finishing touches on my Mk2 suspension parts. I've got a couple coats of gloss black POR-15 on them and they look great. POR-15 does not have UV protection, so they recommend top-coating with a UV protected layer to ensure it doesn't break down due to the effects of UV rays. Being suspension parts they won't be seeing a lot of sunshine, so I'm curious of others experience with leaving the POR-15 as-is without topcoat. Anyone have this on suspension parts with a few years of use that can comment on this? I should note that I also live in Seattle...and while it's not known as the sunniest place in the world (especially this time of year) it is quite sunny in the summer months.
To put a top-coat on I need to rough up the gloss black POR-15, prime with a self-etching primer, and then apply the top-coat. Trying to see if all these extra steps are really necessary. Not trying for a concours restoration but also want the work I put into this to last.
I would definitely top coat the POR15, it's just not worth the concern about UV breakdown later on.
You don't need to rough up the POR15 according to their instructions, either use POR15 high build primer (tie coat) or their self etch primer, you just need to clean the surface first, no roughing required and whack on the primer, then paint with a good quality 1K black .
I do have some POR-15 self etch primer on the way. Their instructions indicate to sand lightly before applying. In hindsight I would have used a less glossy POR-15 to improve adherence of any top coat (primer or otherwise). I used some gloss black that I had around my shop.
I'm curious why they just don't add UV protection to POR-15. The finish comes out really nice and very glossy...seems like putting anything on top of it is a step backwards. Of course this would kill their market for any of their top coat products...
TilleyJon -- your advice is good and that's the direction I was leaning (hence why I had self etch primer and top coat on order). With all the effort I'm putting into this now isn't the time to cut corners. Was trying to avoid a trip down the rabbit hole :-)
If you read the tie coat product info it has a lot more info than the self etch primer info, looks like they didn't expand the self etch info well, it clearly states that you only need to sand for other paint, and that it is fine straight over POR15, and even says that for the self etch primer, but it seems to say that you need to sand it on the self etch info, maybe a phone call or email may clarify as their directions are misleading !
The UV issue is down to it being produced with aromatic urethane rather than a aliphatic urethane, the plus side is aromatic urethane is cheaper and faster curing.
I am not a chemist, but they may have selected the components to give what they deem the best rust preventative results, but cannot also get the UV protection as well ? Either that or it's just a good but expensive system when you take the whole process into account, and they are maximizing their revenue !
Aromatic urethane...that explains the lovely smell in my shop!
Interesting that their directions for Tie Coat actually say to first use Self Etch Primer over POR-15 and then use the Tie Coat on top of Self Etch. Yeah, no mention of sanding. I'll have to give them a call as they have conflicting info out there. If I can avoid the sanding that'll save some time and effort.
Next time I'll use a low-gloss POR-15 as the base coat. While Self Etch may be enough to grab hold of the gloss coat I would think the rougher the better.
Below snip is from the Tie Coat instructions. Thanks for the link.
I just read that snip again, even that is misleading, they say "topcoat with Tie-Coat" as Tie-Coat is a primer it can't be a topcoat as well, surly they should have said prime with tie-coat and then apply a topcoat.
And according to their 2K Urethane info you don't even need the self etch primer and only the tie-coat if you want to smooth out irregularities ! Even more misleading !
And if you don't allow the POR15 to fully cure you can spray the 2k top straight on , at least the paint smells good !!!
http://qr.por15.com/QR-assets/downlo...Directions.pdf
TO PAINT OVER A CURED POR-15 SURFACE
Clean with Cleaner Degreaser as above, then sand with
300 grit sandpaper and wipe clean with dry tack cloth.
Apply 2K URETHANE as final finish.
I used POR15 in the 1990s in some under-chassis parts of my XJ-6. I went through all the ritual.
It was the biggest waste of time and money I ever spent, I could have done the same thing with a spray can of Rust Oelum Industrial Strength Gloss Black.
I used POR15 in the 1990s in some under-chassis parts of my XJ-6. I went through all the ritual.
It was the biggest waste of time and money I ever spent, I could have done the same thing with a spray can of Rust Oelum Industrial Strength Gloss Black.
Thank you, but No thank you to POR15.
That's why i didn't go the POR15 route Jose, despite the hype I wasn't convinced.
When I restored my E Type in 2002, I painted the suspension components with POR15. I did not apply a top coat since there was little or no chance of UV damage.
The picture shows the paint condition in 2016, after 14 years of use at about 1000 miles per year.
I think you will agree that the POR 15 finish still looks quite respectable.
For me I have found good results with POR-15 for the undercarriage but for suspension parts I get them powder coated. To me the suspension parts get more rocks, etc. that will likely chip most paints other than powder coated parts, especially when you drive the car hard and a lot of miles.
01-28-2018, 10:16 AM
Top-coating POR-15 on suspension parts
