Black oxide or Cad plating. Which one is better?  

Sir,
We are manufacturing communication equipments for military. In one of our products we were previously using cad plated skeel screw. Since, our supplier for that screw has stopped doing cad plating suggests black oxide coated as a replacement. Please suggest whether alternate option (blk oxide) will meet our requirement.

Regards,

Well to be honest black oxide really can't replace any type of plating. Black oxide is use on firearms purely for aesthetic purposes. There have got to be a hundred other products that protect firearms better. Black oxide happens to look nice and is rather traditional. Its also used in machine shops as a way to temporarily protect machined steel parts from rust in wrought to its end use destination. I guess in both case's it meets 3 basic criteria. It offers just enough rust prevention to get the job done. It does not alter dimensions enough to hurt anything and it looks nice and probably most important, ITS CHEEP!
The people you should be asking about this are the people that you are making the stuff for. I have had to deal with military mentality off and on over the years and mark my words they do have an opinion on everything. They quite probably had an opinion and an argument the first time you built this equipment for them and they probably spent many thousands of dollars figuring out just why that specific screw had to be cadmium plated.

Rod Henrickson     gunsmith Edmonton, Alberta, Canada

As a follow on to Rod's comments if I was looking to replace cadmium I would probably look at either zinc plating or one of the zinc alloy platings (Zn/Ni, Zn/Sn, Zn/Co etc).

Follow Rod's advice, find out what environment the screw is going to see and judge the replacement technology on that information.

S I D E B A R

January 12, 2010 No disrespect, Rod and Brian, but you guys must not know what you're talking about on this one. I was thinking of getting some titanium nitride coated drills, but decided to go with black oxide after Ryobi promised that it offered "Maximum Durability": The way you guys are talking you'd almost think that companies like Ryobi simply make this stuff up :-) Regards, Ted Mooney, P.E. finishing.com Brick, New Jersey

First of two simultaneous responses -- January 13, 2010

Oh yeah Ted I heard about those. Seems Ryobi is getting them blued on the space station and because of the zero gravity the FE3O4 works its way between the atoms of the material from one side to the other. Seems they only have to blue one side and it works right through the material. You can even re-machine the material and you don't have to re-blue it! They are calling the material Air Soluble Unobtainium! The whole Mars race is based on it as they will pay for the trip by blueing widgets and gadgets on the way there and back. He he he he he

Rod Henrickson     gunsmith Edmonton, Alberta, Canada

Second of two simultaneous responses -- January 14, 2010

Mmm...Titanium nitride or Black oxide... :)

Corr...Unobtainium...how do I get my hands on that? I need some...