Hey, you do realize that a "couple of microns" isn't .0002 inches don't you? It is more like .0000787 inches.
Also, when you say 71 on the rockwell C scale, you don't really mean that do you? The reason I ask is that Rockwell C is a MACRO hardness test. The MINIMUM thickness you can measure using Rc scale is .022inches. Keep in mind this uses a diamond indenter at 150kg load.
Whenever you hear of someone claiming a plated layer in Rc scale, it is that they really don't know what they are talking about. If you doubt my expertise on the matter of measuring hardness of plating, i suggest you go to this link.
Note that I "also contributed". Well, also contributed was that I did the entire article but then left the company so they took credit for it.
For those of you who ask about chemicals that attack chrome, yes there are chemicals that selectively attack chrome and not steel. Same goes for mosty metals. For instance, gold is almost impossible to attack. However, put it in a potasssium cyanide solution and it will come right off while not attacking most other metals.