Most cost effective coating for steel 1

[John2004]

Hello,

I am interested in finding the most cost effective finish for small steel parts that will provide moderate rust protection under normal household conditions.

The parts are farily small and could be machined out of a 2" X 2" cube.

The parts are used on an electric guitar. As far as color, Black will be fine.

Would a black oxide finish be the most cost effective ? Would I need to put some type of coating over the black oxide for additional corrosion protection & if so, what should I use ?

I would appreciate any feedback on the options I may have and any pro's or cons.

Thanks
John

 

[kenvlach]

Seems like a simple question, but too many unknowns for a simple answer.
Do you need a polished look, matte or crinkle finish, abrasion resistance…?

Cost-effectiveness depends a lot upon the quantity of parts. Black oxide shops charge by the pound of steel treated, but minimum job prices correspond to 200-400 pounds.
Black oxide requires an oil or wax for rust protection. The standard water-displacing oil applied by most black oxide shop is rather wet; you would need to wipe down to avoid drips and customers getting oil on their hands. There are dry-to-the-touch waxes available in non-gloss, satin and gloss finishes, but do some asking – probably special order for most job shops.

For best corrosion protection,
1) Zinc plate, black chromate and clear lacquer topcoat or
2) Phosphate (chromate seal rinse), epoxy primer and polyurethane topcoat.

An acid etch-primer can reduce costs by replacing the phosphating and perhaps the epoxy primer. But again, you need a sufficient quantity to justify mixing up a batch of acid etch primer.

For small batches of parts, use the Krylon approach – aerosol cans don’t require air emissions permits.

Consider making aluminum parts and having them black anodized.

Get some line cards from your local metal finishing job shops to find out available processes and pricing. Come back if you then have additional questions.

 

[John2004]

Hello Kenvlach,

Thanks for your reply.

You mentioned making the parts from aluminum and then anodizing them. I can make some parts from aluminum, but there is one assembly that must be steel for strength.

I don't think the aluminum parts will need any finish at all (just a fairly nice machined surface is OK). I think bare aluminum would provide enough corrosion resistance under household conditions.

The main assembly that needs to be steel is a small slider that slides up and down on two dowel pins pressed into a support. Usually the slider is fixed in one position, and only very rarely needs to be adjusted by rotating a small screw by hand.

The tolerance between the dowel and slider holes is very close, i.e, +0.0002" / -0.0000". However, the dowels are black oxide finished, and I don't have to finish the slider holes (they are sparingly coated with a light oil)and are completely hidden. I just need to keep the dowels and sider holes from rusting from a functional standpoint.

Most of these parts are completely hidden within the body of an electric guitar, but a small flat bar or "flange" on the slider support is seen at the back of the guitar body. This piece is only about 7/8" wide, 4.3" long, and 5/32" thick.

I can go with a bare metal look, as long as the parts do not start to corrode or rust.

Initially, I may be doing runs of 50 to 100 pieces, then hopefully more & more (500 to 1,000 or more). The whole mechanism basically comprises about 5 very small parts.

Three parts can easily be machined from a 1.75" X 1.75" X 1" piece, one part can be machined from a 1.55" X 2.65" X 0.5" piece, and one part can be machined from a 0.604" X 4.3" X 0.875" piece.

I thought of using stainless steel without any finish, but even on such small parts, I tend to think the price of stainless may be larger than the price of putting some type of finish on the part ?

I don't need any type of special polished or textured finish and the parts do not need any type of abrasion resistance. As far as looks, a fairly nice basic machined finish is fine.

Most stock rear cover plates on electric guitars are made from plastic with a fairly smooth flat black finish. The steel parts can just come reasonably close to matching the stock plastic parts, but they do not really have to "match" they just need to look reasonably nice and not rust.

You mentioned using wax for additional rust protection. Would car wax provide the needed extra rust protection or do I need a special wax ? If a special wax is needed, can I get it in small quantities and apply it myself ?

Please let me know if this additional information will allow you or anyone else to provide more feedback.

Thanks again,
John

 

[CalculatorDave]

If you expect the aluminum parts to be cosmetically attractive, them you should not leave them uncoated. Handling of aluminum leaves fingerprints. Some individuals' skin oils can actually etch aluminum, leaving fingerprints that won't simply wash off. Better to anodize or coat it.

 

[jdecsz]

Have you considered e-coat?As long as you do not need UV protection, epoxy electrocoating may work for you.

 

[CorBlimeyLimey]

Have you considered polished Stainless Steel?