Coating for A2 Tool Steel

A. Jon,

Anything will work. The question is what additional properties do they want? We used a cold black oxide with a dry to the touch oil on tooling fixture parts with no major problems. A hot black oxide would be superior. I am a believer in EN for tools that get a lot of handling and the numerous resulting fingerprints are not a problem.

A very high probability reason for the zinc blisters is they stayed in the acid activator too long. Which, is really bad if H2 embrittlement is a problem.

A. I don't think it as much the type of plating you put on as it is how the part is pretreated. Find a plater who is comfortable plating on that type of steel.A2 is not easy to plate.

A. While I'm a "wet" plater, I don't think I'm all wet on this response: MECHANICAL PLATING. Millions of pounds of fasteners for the auto industry and others are mechanically plated weekly to avoid embrittlement and problems such as this. There are several sources surrounding Detroit, but it's available nationwide.

Todd is correct (usually is!) on A2 being a difficult to activate and plate alloy; air hardened steels tend to be! Too long in the acid to get the resulting scale off is one of long list of potential sources of hydrogen leading to embrittlement. What was the post-plate bake? Probably should have been at least 24 hours and started within 1 hour of plating. Not soon enough or long enough are two standard causes. ASTM B850-98 has several remarks on this post-plate bake.

Lastly, I'm also a CAD plater, but would steer you away from this coating. The Euros and EPA are doing their best to regulate this coating into oblivion despite its unique and unmatched physical and chemical advantages.

Good luck

A. Jon, if your part is a spring, I'd assume that it will undergo some amount of flexing- and hence I'd avoid coatings that are too thick or too brittle. The black oxide that you and James mentioned would likely be my first choice.