[R-390] Painting Knobs

[Barry]

Tom, 

I really wish I had glass bead or other media blasting available. That would have saved me so much time! 

After getting as much of the existing paint as I could with Aircraft Paint Remover, I resorted to hand-sanding with 320-grit silicon carbide paper. That left a shiny but not too slick of a finish. I really don't know why the primer didn't stick to it. 

I went with full gloss and not sure if that was the best choice (I don't remember what sheen I used long ago) but it looks okay. If this paint job does fail with use, then at least it's easy enough to remove... 

Thanks again, 
Barry - N4BUQ 

> Barry,

> I have done several sets and just finished up one the other week. I used to wire
> wheel the old paint of but have since transitioned to using my glass bead
> cabinet. This provides a little "texture" for the paint to grip to but not
> enough to show through to the finished coat.

> I have also used the self etching primer with good results. For the last two
> sets I used Rustoleum semi gloss / primer in one. This worked well also.

> Tom
> W3TA

> On Monday, August 12, 2024 at 10:13:31 AM EDT, Barry <n4buq at knology.net> wrote:

> As I've mentioned over the past several months, I'm in the process of
> refinishing the knobs (as well as all the other front-panel parts) for my R390.
> I stripped, sanded them and used Rust-Oleum Self-Etching primer and painted
> them with Rust-Oleum enamel.

> The Rust-Oleum Self-Etching primer and Rust-Oleum enamel worked very well on the
> front panel, escutcheon, meter covers and, as far as I know, the large knobs. I
> had reason to remove the paint (again) on the larger knobs and the paint and
> primer stuck quite well; however, I've discovered that the primer doesn't seem
> to stick very well to the smaller knobs.

> While working on the smaller knobs, I noticed a small chip in the paint on one
> of them that exposed the bare metal. I don't know exactly how that chip was
> made but I think I dropped one of the knobs onto the table top which might have
> hit it just right. I noticed I could take a sharp putty knife and some of the
> surrounding paint could be removed all too easily. Another knob had a very
> small spot where the bare metal was exposed as well.

> I decided to dump those two (and a third one that had some small defects in the
> top coat) into a can with acetone and, after a short soak, I pulled them out.
> The paint had wrinkled quite well and was very easy to remove (it virtually
> fell off); however, the primer also came off very easily which was different
> than some of the other pieces I'd painted. In fact, the primer and paint stuck
> very well to each other but the entire paint/primer fell away from the metal.

> I think those knobs are die-cast aluminum so I can't explain how/why the primer
> wouldn't have stuck to those the same way as the other aluminum parts but I
> just don't know.

> Anyone have a similar experience and, perhaps, have a suggestion for a better
> primer? I think the factory used conversion (Alodine?) process on most all of
> the aluminum parts and that would probably be a "best" solution. I had some
> parts done that way many years ago around here but it was pretty expensive and
> I'm not sure it's even still an option around here.

> Thanks,
> Barry - N4BUQ
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