Q: Using POR-15
I’m considering doing the front rails and vaious suspension bits. How did you prep. the parts ?? Sandblast ?? Did you use the POR topcoat or just the rust-preventer ??
A: The POR-15 vendor I deal with strongly suggests sand or bead blasting items in preparation for painting for the smoothest finish, and best adhesion. If you do media blast, then the metal prep is not required. I’ve also wire brushed or sanded a number of parts or surfaces that weren’t practical to blast. For those items, I did use the metal prep to etch the metal, and to further kill/stop any rust.
I have found that if the POR-15 paint is used as a top coat, it will discolor if exposed to UV light. Most parts under the car are not a problem, but parts of my subrame are showing the dulling/discolorization now. This shouldn’t apply to their Chassis Black paint. But I’ve found that this paint must be sprayed on. My experience using a brush was less than great.
As for brush marks, this is a problem. Using a foam brush cuts this down, but the brush has a tendency to fall apart eventually. For parts that I want a very smooth finish, I coat with POR-15 (two coats), then dust with a primer. Once the POR-15 has cured, I then do at least another coat of primer, then spray a top coat of the final cover using an enamel or other paint of choice. This usually covers the imperfections left by the POR-15, and prevents the UV discolorization.
Prior to getting my car painted, I removed the subframe, cleaned and prepped it, and painted (using a brush) it with POR-15. It came out quite nice, and then I bolted it back on and sent the car to the body shop. When it came back, the subframe was covered with sanding debris and overspray from the bodywork process. I had to sand that off and coat again with POR-15 to get it smooth again. The Catch 22 there was that since the new front sheet metal was bolted on the car at the body shop, the only time to prep the subframe was before the body work. I think that I should have pressed the shop to take greater care in protecting the subframe. Now I know better.
Content last modified: January 7, 2014 at 8:06 pm