Surfaces that are really shiny (like Octane shoebox and PSU) normally don’t have “brown rust” they have white rust. White rust is going to be a different recipe.
But if you really have brown rust spots, and the entire surface is kind of dull and pitted, then there is no hope of it every being shiny without some kind of false chrome painting and clear coat after restoration (I’ve not tried this).
If you really do have a Octane shoebox that is best described above then doing this cold galvanized zinc coating is an option.
Please note several issues:
The surface needs a fair mechanical sanding, without gouging, using a very fine sanding disk or wire wheel (I used a fine Dremel brand wire wheel) to remove the rust color and gently go over the dull-pitted surfaces. A fine wire wheel is what you want, not a course one. You don’t want deep scratches as they will show after painting.
For card cages I’ve seen, the inside is just as bad as the outside, so consider if you want to remove everything and attempt a more full coverage, I know most of it is riveted, so it’s hard.
You can use a HVLP sprayer with this product as-is. Air spray requires thinning with a solvent. I bought so little of the product that I’d loose a lot of it trying to properly prep the coating for air spraying such a small area. So I used a brush. However you’ll see the brush strokes in the coating, there doesn’t seem to be a way to avoid that, spraying will be the only way to coat without brush strokes.
If I had a cheap HVLP sprayer, I might have tried it if I can get all my metal together at once to spray (again due to loss in the sprayer and such, I’d be cleaning out more coating than what I sprayed).
Mix/stir like your arm wrestling the devil back into the underworld when mixing this coating. If you still feel sludge at the bottom, then you need to get down there an mix a lot more. Use a drill, seriously this stuff may look like paint but it is not entirely paint.
I used acetone after sanding the region to make sure it was clean. The instructions for the product are vague and say they prefer a chemical etching but often mechanical means works fine.
Also please note this is supposed to be the lighter color of the two products and it’s still fairly dark. I’m pretty sure you can paint over this stuff once fully cured. So it may be possible to use an shiny metal spray paint and then a clear coat over this stuff. It may require a primer.
Since only a little bit of the shoebox sticks out of the back, you could try to do a 360 degree paint of the end that shows with the expectation of also using a fake metal paint in it too for visual affect. But again, I’ve only tried what I posted and I’m not adept at painting so perhaps consult a professional automotive painting shop after you’ve zinc coated for some options?
Let us know if you decide to pursue this.
(10-09-2021, 04:16 PM)robespierre Wrote: The simplest rust-removal techniques are wire brushing and naval jelly. A brush with steel bristles is harder than rust, so it scrapes away rust without harming the steel underneath. Always use a wire brush with bristles equal or softer than the workpiece so it doesn't get scratched. Never use steel bristles on aluminum or copper: only brass bristles.
Naval jelly is a mix of phosphoric acid with a cellulose gel so it sticks to metal. The acid removes some rust and converts the rest to black iron oxide, which doesn't flake off or spread. After using it you rinse with water to remove the acid.
Another unusual method of removing rust is using ammonium thioglycolate (hair perm salt). It is not acidic but dissolves rust and turns bright purple at the same time.
A problem you will run into with most forms of rust removal is that with its protective oxide layer removed, steel can rust very quickly. This is the so-called "flash rust". To stop it you need to apply protection within an hour, the quicker the better. For example, if you use naval jelly, after rinsing you need to dry the metal as fast as possible and then apply your protective coating.
Protective coatings fall into three broad categories, the oxygen barrier layers, sacrificial galvanizing metals, and chemical corrosion inhibitors. Oil and grease are barriers and work quite well for protecting things like hand tools. Zinc is a more active metal that provides galvanic protection. Generally the steel cases were coated with molten zinc in a process known as hot-dip galvanization.
Zinc-rich paints are much less effective than hot-dip galvanizing and the difference can be seen easily on a photomicrograph. But they are a method of repair that is within the reach of normal people.
Yes, I live around several platting businesses but chose not to pursue having the entire power supply re-platted and everything due to cost. When these power supplies are $700 a piece (retail) I’ll be happy to totally remove the old coating, heavy electroplate a new one, and have custom stickers printed to replace the old ones on top, along with all the electronic rebuild parts and labor.
But not for ~$200 ish final value. Even if I batch them all at once I’d have more into them than anyone would pay. Perhaps for my personal collection I might, but I doubt it.
Considering my hope is, the new owner doesn’t place these in an uncontrolled outside environment, the zinc is overkill for indoor use, but that’s better in case it once again gets put in an unheated garage or something.
However, perhaps getting a quote from a business for that Octane card cage wouldn’t be so bad. If all the electronics and fan can be safely removed and it’s less than $400 after tax to strip and restore the shiny surface, perhaps that’s better then coating with since a shoebox is worth more than an Indy PSU and the value will only increase. So perhaps it makes more sense then?
NEED -> 
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