Do I have to prep Por15 before Primer?

Kroggers · Kroggers's Garage

I have painted the base of my car with Por15, and will cover it later with Por15 Self Etching Primer. But this is where the instructions are confusing! On the Por15 Website, they state that the Por15 SEP can be painted directly on cured Por15 with no preparation, whilst on the tin they recommend sanding any paint first?

I do not plan to paint the SEP for a month or so, as there are other parts of the car that I will paint with Por15 first (thought I would do the primer all in one go). Do I have to sand the top of the Por15 or can I just paint the Primer directly on with no prep?

evill · evill's Garage

The POR SEP will stick directly to the cured POR 15 w/o sanding.

Personally, I still like to prep the cured POR 15 with a red scuff pad prior to top coating with POR SEP.

Ed

Kroggers · Kroggers's Garage

Great, thank you Ed. That is good news

scottbooth · 02-21-2007, 04:41 AM

Hi Pål

How much POR15 did you need to paint the underside of your car?

I am still removing undercoating and PVC looking for rust (not much found so far, which is good) and plan to reseal it all with POR15 when I am done. Not sure how much to order and it would be good to have enough (but not too much) when I start.

Thanks
Scott

Kroggers · Kroggers's Garage

Hi Scott, so far i have only done 50% of the car. I have done the front end, and gone half way under the car. I will do the back end when I strip the rear end for the suspension rebuild etc.
What I did was purchase the boxes with 6 small tins in them. For what I have done so far I used 2 small tins of silver for the base and 3 small tins of black. I figure I have enough silver, but will require 3 - 6 more small tins of black.

I know it probably would be cheaper to get the bigger tins, but I felt the storage of tins that had been opened was a pain (keep cool and all that)

As for rust, apart from the front bumper shock mount (in my other thread) and the driver side jacking point which will need some work, I have only found small patches here and there that can be just covered up with the Por15.

evill · evill's Garage

It spreads out really well with good coverage. I did the interior, floor pans, back seats, rear package shelf and front trunk area of my 911 with a little less than a pint of black POR-15. I very rarely use more than a qt on a restoration.

Ed

scottbooth · 02-21-2007, 04:58 AM

That is good news on the rust. I read your thread about the fender repair (looks good). You are doing a nice job on your car, and are several weeks ahead of me. I think we are headed for the same place.

I have some rust in the same spot but think I can get away with a much smaller patch. Then again I haven't really torn into it yet. I figured I would check the rest of the tub before I started fixing things, just in case the problems got out of hand. I finally took some pics last night and will start a thread on my project soon.

I have seen others use coats of silver and black. I assume the point there is to make sure you get 2 coats of coverage without missing anything? Or is there something more to it?

Thanks
Scott

scottbooth · 02-21-2007, 05:01 AM

Thanks Ed. I am planning to do my interior and trunk along with the underbody. Maybe I will just buy a quart and try to do the job all at once so I don't need to worry about storing the unused portion.

Did you put on one coat or two?

Thanks
Scott

evill · evill's Garage

Scott, I used 1 coat since was for cosmetics and protection. If you have rust ot areas that you want extra protection, 2 coats is good. You really do not need more than that.

Ed

Kroggers · Kroggers's Garage

Scott, the silver is a thicker paint to give a better finish over rust.

scottbooth · 02-21-2007, 05:37 AM

Thanks guys. Good info.

Scott

petrolblue83911 · 02-21-2007, 08:53 AM

just curious,

i've used por 15 for non cosmetic areas where I left it without primer. these areas still look perfect many years later. Why then would you sand the base-coat? I understand that it may give the primer a better foot hold but I would be afraid that you would reduce the corrision resistance, which in the covered areas of your front end you won't be able to see once the trim is re-installed.

Kroggers · Kroggers's Garage

Quote:

Originally posted by petrolblue83911
just curious,

i've used por 15 for non cosmetic areas where I left it without primer. these areas still look perfect many years later. Why then would you sand the base-coat? I understand that it may give the primer a better foot hold but I would be afraid that you would reduce the corrision resistance, which in the covered areas of your front end you won't be able to see once the trim is re-installed.

First off, Por15 is sensitive to UV light (sun) and must be topcoated for prolonged exposure to sunlight.

Secondly, the addition of primer and another layer of paint gives additional protection.

And as a last point, I want to top cote with the same colour as the car to give it a nice finished look. Just because it is not visible to others, I will know it is not perfect