Long version:Short version:
I've been planning on getting into metalsmithing to be able to make rings and such. I don't really want to bore you with all the details or anything but since gold is so expensive and PVD's, even something like TiN or ZrN(C) will eventually wear off under years of heavy use, I figure the only real solution is to use an alloy and the only promising alloys seem to be some derivatives of copper like manganese bronze, silicon bronze, C954 aluminum bronze but even those with their superior corrosion resistance are probably going to leave a green mark on your finger or smell like vinegar from the chemical reaction with heavy use. It really makes me wonder though why something like a stainless brass/bronze doesn't exist.
The main question I've actually registered to ask is if you could add a significant enough (minimum of 10.5%) level of chromium to bronze (or a similar copper alloy) so the chrome oxide would do for bronze what it does for iron in stainless steel and essentially create a stainless bronze.
First before I get into all of the complicated details allow me to explain the situation: I'm looking to get into metalsmithing to make my own unique custom jewelry because it seems like it would be a fun and rewarding hobby.
I've never really been a fan of white/grey metals. My only real love when it comes to metals are the ones in the red yellow (Au) spectrum:
Essentially, gold. The ideal color being the color in the center here:
So now that we have established the color we have to get into the specifics of things. Gold has all of the properties as a noble metal and availability that it's clearly the best choice at this point but let's face it: gold is expensive. It may not tarnish but the materials for a single ring would set you back some $300-600, if not more, and I've never personally cared about the prestige of jewelry. I know that it is important to some people that their piece of jewelry is expensive and they can proudly wear it as a status symbol. Personally, I worry about something that expensive being stolen or losing it. For me, jewelry is all about aesthetics: "Does it look beautiful?," not "is it expensive?." For instance, I would choose moissanite over diamond any day because it's far more brilliant regardless of the status quo where everyone thinks diamond is the must-have gemstone. And of course rather than an obscenely expensive ruby I'd go with a red (pyrope) garnet instead - they're dirt cheap and still very beautiful.
But beyond that, it also needs to be functional. Nobody likes gold plated jewelery that wears down or chips on them revealing a different metal underneath. It's cheap and it's really not desirable. So it needs to be both the color of gold and also functionally similar in that it won't tarnish nor reveal a different color after heavy wear, or damage, and it can't smell or leave a mark on your finger.
What I'm after isn't just the color gold. PVD's, even something like TiN or ZrN(C) (where the amount of carbon is used to adjust the color) will eventually wear off under years of heavy use or potentially get scratched. I figure the only real solution is to use an alloy and the only promising alloys seem to be some derivatives of copper like manganese bronze, silicon bronze, or C954 aluminum bronze; but, even those with their superior corrosion resistance are probably going to leave a green mark on your finger or smell like vinegar from the chemical reaction with heavy use. I suppose you could perhaps use something like C954 aluminum bronze with a ZrN(C) PVD to help negate ever noticing if it wears down or becomes scratched.
Choosing the gold color almost feels like self flagellation at this point as working with something as popular and readily available as stainless steel or titanium which are already well established would be a far easier task. Even silver, really. It's far cheaper than one would imagine despite its grouping as a precious noble metal and listed commonly right along with gold - you can get a silver coin on eBay for $6-12. Heck, I saw a set of ten 90% silver dimes going for just $20 yesterday.
So this leads me to the question: Surely someone else before me has thought of this and felt the same way. So why doesn't something like a stainless bronze exist?
Let's look at another stainless metal: stainless steel. Steel is essentially iron and carbon, what makes it "stainless" steel is a minimum of 10.5% chromium. So, shouldn't we be able to add a significant enough (minimum of 10.5%) level of chromium to bronze (or a similar copper alloy) so the chrome oxide would do for bronze what it does for iron in stainless steel and essentially create a stainless bronze?
I admittedly don't know much of anything about metallurgy. But, maybe one of you guys can help me out.
Darryl was kind enough to send out a mail to the guild's jewelers and metallurgists asking this very question (short version), but I figured that it might be good to have it here officially on the forum.
Here is a reply from Herb:
Herb wrote: It seems she is asking for alloys that are used in the electronics business.
Some of these corrode, but not all.
I could suggest she look at thermocouple tables, or go the web sites of Isabellenhuette, Dillenburg, Germany.
They probably make half of the thermocouple wire used in the world.
They build their own ingots, produce wire and foil, and sell thermocouple wire and precision resistors.