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need to paint a hinge black ... start with stainless or unfinished steel

need to paint a hinge black ... start with stainless or unfinished steel

need to paint a hinge black ... start with stainless or unfinished steel

(OP)
I need to use a tight clearance piano hinge, and paint it black. McMaster gives me 2 options: 304 stainless and "unfinished steel". See here:
http://www.mcmaster.com/#piano-hinges/=x6k7dv

From which would be easier to apply a durable black finish? Also ... needs to be a fairly thin coat, as there are tight tolerances on the hinge's moving parts. Recommendations on a durable finish? I was thinking POR15, but didn't know if it would adhere better on SS or regular steel.

RE: need to paint a hinge black ... start with stainless or unfinished steel

Anodize it.

RE: need to paint a hinge black ... start with stainless or unfinished steel

I tried a "white" primer on a similar piano hinge below a final black coat. Also tried a grey primer (automotive type primer.)

It didn't work at all. Had to remove it, tried again with a black primer and black cover - still rubbed off, but pretty irregularly. Not real happy with any of the other things I tried either.

So, you're starting off: Try a black oxide base, then as light a black cover coat as you can get away with. A chrome or polished steel hinge makes it worse.

Outside? Corrosive environment like a salt air or a food service area where lots of cleaners get used?

RE: need to paint a hinge black ... start with stainless or unfinished steel

Hinges aren't meant to be painted.

RE: need to paint a hinge black ... start with stainless or unfinished steel

Anodizing is for aluminum.
The associated acids will not do steel any good.

There is, or was, a mil-std process for producing black chrome plating, originally intended to reduce the observability of missile launcher rails. I'm not sure that I've ever seen it in use.

Plain steel can be cleaned and given a 'black oxide' coating. Some of the blackening processes are done hot, some are done cold. It works best against corrosion when post-treated with oil.

Nowadays, when I think of a tight black hinge, I think of a Southco product that's made entirely of plastic, is pretty damn strong, and can be tightened so it will hardly rotate. ... but it's a 3-inch-ish long leaf hinge. There is no corresponding piano version of which I am aware.

You could buy a black vinyl extruded hinge, and bolt it down with a doubler, but it's sort of ungainly for exposed applications, which I assume is the root of the black requirement.





Mike Halloran
Pembroke Pines, FL, USA

RE: need to paint a hinge black ... start with stainless or unfinished steel

Stainless steel can be anodized. Paint won't last on a hinge. As hokie66 noted, not really meant to be painted.

Mike...I like your idea of blackening the steel. Nitriding is one method of doing that. Another consideration is "blueing" as in gun barrels. Finish is almost black!

RE: need to paint a hinge black ... start with stainless or unfinished steel

Aluminum is anodized by passing an electric current through it from an acid electrolyte, thereby converting a few mils near the surface from aluminum metal to aluminum oxide, which is a hard ceramic. Anodize is inevitably microcracked, so it is post-processed with a sealer so 'white rust' does not appear. The sealer often also carries a dye. The dye is available in a fairly wide selection of colors.

Passing an electric current through a steel article in an acid electrolyte will dissolve the steel even faster than the acid alone would do. Stainless steel would resist the acid attack a little better than mild steel does, but the nice glossy mill surface would certainly go away. The reaction products would include one or another form of iron oxide, all of which are of colors not usually associated with stainless steel.


Magnaplate Co. has a process for making aluminum wear resistant by anodizing it to a relatively substantial depth, and filling the microcracks with polytetrafluoroethylene, condensed from a gaseous state.

Their corresponding process for steel involves first plating the steel with microcracked nickel, then filling the microcracks with PTFE as above.


If someone claims to be anodizing stainless steel, I'd sure like to learn more about who they are and what they are actually doing.



Mike Halloran
Pembroke Pines, FL, USA

RE: need to paint a hinge black ... start with stainless or unfinished steel

Mike...Russamer Labs has stated that they can anodize SS. What you said makes sense, but you might check with them to see if that is correct.

What about a conversion dip?

Also, how do the knife manufacturers produce the rainbow coloring on SS knives (Kershaw for example)?

RE: need to paint a hinge black ... start with stainless or unfinished steel

It appears that Russamer can apply a fairly durable colored coating to stainless steel. The available colors suggest that they use dyes similar to those used in anodizing sealants.

That alone is no reason to usurp the word 'anodize' to describe whatever process they use, which is not disclosed.

I'd be hesitant to specify it for anything just yet, as it appears to be a new process, and the website contains a lot of, ahem, 'forward looking' language.


WRT rainbow coloring, this from a Kershaw page:
{
This Kershaw Ken Onion Rainbow Leek, Model 1660VIB, has a titanium oxide coated 440A stainless steel 3 inch blade and handle. The rainbow colors are created by passing currents of electricity over the coating using varying intensities.
}
... so the color is in the titanium oxide coating, not in the stainless steel.

Mike Halloran
Pembroke Pines, FL, USA

RE: need to paint a hinge black ... start with stainless or unfinished steel

Heat and various chemicals have been used to color metals for millennia. Some recipes are lost to antiquity, some have been commercialized, some are preserved in Machinery's Handbook.

I have had good luck with generic gun blue, and with a couple of different Birchwood Casey products.

... most of which don't do much to stainless, but will work nicely on carbon steel.

The most important part of the process is getting the steel really super clean, and then doing the blackening before it rusts, and oiling the blackened part before it rusts.

I have found that regular Brakleen in the red can does pretty well as a degreaser.

Keep the soup off your fingers; otherwise they will stink and retain some ugly color for weeks. ... This I know.

For something as awkward to handle as a piano hinge, you don't need to use (and fill) a big tank. Just find a really long polyethylene bag in which to conduct the process with a few ounces of liquid, and keep the liquid moving so the poly can't isolate the part from the soup.


Mike Halloran
Pembroke Pines, FL, USA

RE: need to paint a hinge black ... start with stainless or unfinished steel

Thanks, Mike....Kershaw knives are my favorites but don't particularly like the colored ones. I like the nice clean stainless ones.

RE: need to paint a hinge black ... start with stainless or unfinished steel

(OP)
Great input. Thanks!

RE: need to paint a hinge black ... start with stainless or unfinished steel

There is no type of "durable black finish" that can readily be applied to a mild steel or stainless steel piano hinge assembly. Plating or painting will only be able to coat exposed surfaces and not those having close fits to other surfaces. To do a proper job of coating you would need to disassemble the piano hinge parts and coat them separately.

RE: need to paint a hinge black ... start with stainless or unfinished steel

First perform all of the machining operations you need to do on the plain steel piano hinge assembly. Then disassemble the piano hinge by removing the hinge pin. Then have the hinge parts plated with a thin coat of black EN. And then re-assemble the plated hinge parts. The plating thickness will only be about .0002-.0003", so it should not have a significant effect on the hinge part fits. And since you will have done all machining operations prior to plating, all of the hinge surfaces will be protected.

RE: need to paint a hinge black ... start with stainless or unfinished steel

(OP)
What is black EN?

I've been thinking of going with the SS and this caswell plating:http://www.caswellplating.com/metal-finishing-solu..., although I'm not sure this will give me as dark as I want (more of a bluish grey I believe) and suspect that I'd get much darker with soft steel ... but any black-oxide on soft steel will eventually rust (it will be frequently touched with hands), which isn't an option as I'm doing this for a customer and don't expect them to apply oil every couple years to it.

I think I could get the darker oxide if I did a hot sodium hydroxide / nitride dip on the SS, but I'd have to send it out for that and then prices start really escalating at that point.

RE: need to paint a hinge black ... start with stainless or unfinished steel

Black EN is black electroless nickel.

The black oxide coating you describe will not provide much corrosion protection on mild steel, and it should not be applied to stainless steel assemblies like your hinge where the process fluids cannot be completely flushed from tight-fitting interfaces.

As I suggested above, your best option would be to first perform all machining/trimming operations required on the assembled hinge. Then disassemble the hinge. Apply the black electroless nickel coating to the hinge leaves and pin. And then re-assemble the hinge parts.

RE: need to paint a hinge black ... start with stainless or unfinished steel

(OP)
Great points, thanks - do you know typical costs for EN Black? Looks like a pretty awesome finish with great qualities, but it also sounds like in order to get it a nice black color, parts need to be polished first.

Keep in my my best option is also to get the biggest bang for my buck as this is coming out of my pocket and this is a small part on a much larger and very involved product off which I only make $500 a piece. The margins are already pretty tight.

That is why I'm thinking of trying a number of things on a number of hinges, with cost being as important as cosmetics.

Also, the hinge is used only for setup, which doesn't occur more than say 1-2 times per month on average, so wear is not a huge concern.

I'm not really considering mild steel at this point either.

Thanks!

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