Sanding to bare metal

[mcmanucr]

Hey Guys,

I'm going to start a trailer restoration project in a few weeks and need some help. I have researched BBC extensively and decided that I'm going to sand to bare metal and most likely apply Por15 but am also thinking about a bed liner type material. I am new to sanding metal and just used an angle grinder with a wire brush as well as a 60 grit flap wheel. I had two different results and am hoping you could tell me which one I want. Both tools removed paint easily but the wire brush left it dull and the flap wheel left it shiny. Which one am I looking for? I have inserted two pictures so you can see what I'm talking about. Any help would be greatly appreciated.

[NJBass12]

I just restored my trailer earlier this year. I used an angle grinder with a wire brush on areas that had rust.
The rest of the trailer I hit with 60 grit sandpaper.
I followed up with two coats of primer and then a bed liner.
End result was great. I've had no issues so far.

[dnolen]

If you want to take it to metal. I would but a cheap sandblaster or have some one sand blast it. If the boat is not on it. It should not cost much. We have a local shop that sandblasted our 16ft trailer for 250.00.

[mcmanucr]

I wish I could find someone to blast it for that price. Cheapest I have been quoted is $1200. From my understanding sandblasting makes a pretty big mess so I don't think I could do it with the space I have.

[David g]

As the owner of an aircraft painting facility for many years, we painted mostly on aluminum but the older and better Cessna steel spring gear was what it was. We always stripped the aluminum using a chemical ammonia based paint stripper to get as much paint removed around rivets as possible to achieve adhesion. Cannot sand rivets because structural integrity is compromised so if we had remaining paint not removed by chemicals, we used RolLok discs made of nylon on an angle grinder to complete because is doesn't damage the aluminum surfaces. Ferrous metal areas, while scarce on an aircraft, were sanded using a DA sander.

Really no reason to sand to metal as long as the existing paint has good adhesion. It the old paint is stuck, sanding smooth, priming and then topcoat works just fine. You can grind all you want on the paint but you will not remove all of it on the inside of the channel iron unless you abrade blast or chemical strip. And, no need to remove all of it as long as it is smooth and stuck. Removing to the metal also will present an opportunity for rust to start under the paint unless you use a conversion primer.

All of this dialog is to point out that removing to metal may not add value to your job and may also introduce rust to the equation. I would use a conversion primer regardless of whether I sanded to metal or not because there will always be bare areas where sanded through paint to invite rust. 180 grit 3-M paper on a DA should provide a good base for priming. Main thing is surface smooth (use your fingers, not your eyes) and clean....clean, clean. And did I mention clean? Use a strong cleaner like "Superclean" (O'Rilleys) and follow with prepsol and use a tack rag befor spraying.

[billnorman1]

^^^like I said, good old paint is a good start for repaint if clean and roughened.