Re-finishing Farnell L30-1 Power Supply Case - recommendations ?

[Goldie99]

I recently purchased an older Farnell L30-1 power supply, that after a little minor fettling is now working perfectly. The case and part of the front 'bezel' however are showing their age. I can 3D Print a replacement 'bezel' to tidy that up, but would appreciate ideas for re-finishing the outer metal case, which is a ca. 1mm sheet steel (?) painted with a Farnell textured dark grey finish ? It doesn't 'feel' like a finish that'll readily succumb to paint stripper, but I'm sure someone here will have experienced similar previously.

The pics below show the present sort of damage, which doesn't wash off, so I assume is some kind of corrosion. It almost resembles the corrosion you get on Aluminium surfaces, but the case itself feels more like steel.



Cheers, Alan

[G6Tanuki]

There is a local place that does powder coating, they also have sand/soda-blasting facilities. Most of their customers are restoring old cars or motorbikes, but the guy who runs the place will blast small items at his convenience (sticking them in the cabinet with something else) in exchange for a few beer-tokens.

Same guy will etch-prime, twin-pack, powder coat or Rilsan small things on a similar basis, though you may have to accept a restricted range of colours because he will be using up whatever is left in the gun after a full-price job.

[Uncle Bulgaria]

Check it with a magnet. That looks like zinc alloy corrosion of the sort seen on certain camera bodies. If you want the same effect, you could try a wrinkle-finish spray paint as used on old car steel dashboards. I haven't had much luck with paint stripper on metal, and for large flat surfaces much prefer an angle grinder with a non-woven pad on it. Takes paint off in seconds.

I dislike powder coating for the tendency to chip, especially round screwheads or holes, and it's impossible to repair, so I've got into Paragon enamel paints for machine tools as easier for the DIYer.

[fetteler]

I'd say that the case is aluminium and that the white stuff is aluminium oxide but even if it is zinc oxide I wouldn't worry or stress too much about it. The best thing to do is give it a good rubbing over with a Scotchbrite pad to remove any powdery oxide then simply respray with a matching colour. What with the original finish being randomly textured you will retain most of that texture and the corroded bits will fade into the textured background.

You almost have nothing to lose by giving this a go before trying anything else. It will be inexpensive to do and my gut feeling is that the end result will be really good.

Steve.

[ajgriff]

Following on from Steve and UB's suggestions this might produce the sort of finish you are looking for:

https://www.ebay.co.uk/itm/392912699573?_trkparms=amclksrc%3...&itmmeta=01K5N0A69118CGKPVGXXPF5Q9N

Interesting that the earlier L30 had steel panels with a blue painted hammered enamel finish.

Alan

[Goldie99]

Cheers guys - all good ideas. I just quickly checked with a magnet (should have thought of that !), and it is indeed steel, maybe zinc passivated ?

Unfortunately I don't know any local powder coaters at the moment, but that's certainly one I keep revisiting, often for similar type small paint jobs, so I do need to put more effort into finding one I think.

In the mean time though, I do like the Scotchbrite & respray option. As Steve says, nothing to lose, and everything's in the garage except the paint.... but I think Alan may just have nailed that one too !

Thanks, Alan

[Goldie99]

Originally Posted by ajgriff

Interesting that the earlier L30 had steel panels with a blue painted hammered enamel finish.

Not sure how relevant it may be Alan, but it's a fairly early L30/1 (full discrete transistors, and ser. # 000943). It's an ex. RAF Halton Training unit, which might explain the colour. Your suggested paint option is ordered in the mean time.

[Goldie99]

Quick update - I ordered a can of the so-called "Slate Grey" paint Alan referenced in post #5 above, and unfortunately have to report than it is far from a "Slate Grey", and is much too light in colour to be of use for this job.

I've had it refunded already, and will pursue alternative paints. The Scotchbrite option has already worked quite well, and removed the vast majority of the corrosion.

Alan

[fetteler]

I expect that respraying with a non textured regular paint of the correct colour and lustre will do the trick. Now that you have got rid of most of the corrosion the texture of the original finish should 'shine through' the respray.

Steve.

[Goldie99]

Just to close this one out - the re-finished article. The Scotchbrite & respray with a std. gloss finish worked extremely well, the colour I used in the end was a 1k DTM aerosol, RAL 5008 ("RAF Grey-Blue"), from eBay.

A slightly more expensive paint option, but it did have small areas of bare metal showing, and it's covered very well, this has had just 2 light coats, and a couple of hours in the oven.

Overall, a beautiful and seemingly tough finish, and although it's not a perfect colour match to the Farnell original, I actually prefer the RAF colour.



Thanks again esp. to Steve, I'd never have thought of the Scotchbrite !
Alan

[ajgriff]

Nice job. Looks really good.

Alan

[G6Tanuki]

That's worked out rather well - preserving the original textured finish and discreetly covering up the corrosion induced pitting.

Nice job!!

[fetteler]

WOW!
That looks absolutely smashing Alan, what a great result.

Best wishes,
Steve.

[Diabolical Artificer]

Looks swish Alan, cracking job. I have a L30/5 that needs doing, I'll check that paint you used out, not cheap @ £18 but you get what you pay for. Did you use an etching primer?

Andy.

[Goldie99]

Hi Andy - no etch primer, just Scotchbrite, solvent wipe down, then paint. I've pm'ed you the eBay seller I used (£15.99 incl.).

It wasn't cheap, but it covered very easily with just 2 light coats, so plenty left.

Cheers,
Alan