Finishing Fiberglass And Aluminum


From original questioner:

I have a fiberglass and aluminum industrial electronics panel box to finish. I was going to use Clawlock and the Resistant to finish the box. Campbell informed me that they only test on wood. Does anyone know if the campbell products will work. If not can you recommend a finishing product.


From contributor ch

go to a car paint supply store.

From contributor Ji

Auto epoxy primer is the best choice

From contributor Ni

PPG's "Breakthrough" might be what you're looking drying WB for an array of substrates including fiberglass and aluminum (although aluminum requires priming first). It has very good adhesion and blocking for a WB.
I used some the other day for 18 display pedestals used to display furniture...painted them on a Tuesday, set the furniture (dinettes, couches, benches ect...) on them Thursday evening and no sticking.

From contributor Pa


Acid catalyzed finishes (e.g., pre-cat and CV) do not work with metals. And some finishes that are advertised to work with aluminum do not perform very well.

I like Jim Clark's recommendation to use an epoxy primer. Instead of automotive brands, I use a LOT of the Matthews catalyzed polyurethane products marketed to exterior sign makers (see link below). Their high build PT filler primer works great on aluminum as well as the epoxy. But the epoxy primer is more versatile and works with a much wider range of substrates. The epoxy primer needs at least 2 hours before you can sand it.

Make sure you read and follow the tech data sheets for any of these products and adhere to the same safety precautions you would use for any 2KPU.

FYI - for MDF, especially glued-up layers with exposed edges that need a lot of filling, the polyester primer does a great job - very high build - but very short open time once mixed.

From contributor Ma


I have sprayed many radiator covers with aluminum grills, which have been random orbit sanded and de-greased, with acid catalyzed finishes. I have several in my own home that are 3-5 years old, and have noticed no issues. The finishes were from Conestoga (Valspar and now Sherwin Williams) white catalyzed “paint” with CV topcoats.

Is there any reason that I should be concerned?


From contributor Pa


The main concerns using acid catalyzed finishes on metal are discoloration and poor adhesion. It sounds like your finish is performing well - which is lucky. Some acids and resins do much better than others....

Always read and follow the tech data sheet for the products you're using to avoid potential problems.

With aluminum I've learned to do both short term and long term adhesion testing of both coatings and adhesives. Some seem to work well initially, but after several weeks or months start to fail.

From contributor Ma

Thanks Paul,

I’ve had no issues with discoloration and in all cases the finish has been white on the aluminum radiator grill, solid wood and MDF that was used to fabricate the covers.

I carefully prepared the aluminum with sanding and de-greasing and I am sure that this has led to superior adhesion. The only place I can say that I have had a slight issue is where my daughter made a very sharp crease/dent in the grill. When I flattened it back out I got some cracking of the finish, but no flaking. I assumed that most finishes would have done the same.