Plating specification QQ-Z-325

A. I only can find QQ-Z-325C which is classification

one  Thickness  25 µm  or 1.0 mil
two     "       13  "  or 0.50 " 
three   "        5  "  or 0.02 "

Class  mil        External   Untreated 
                  threads    surfaces
0.50   0.1-0.4    0.2-0.5
1      0.1-0.3    0.1-0.3    0.2-0.4
2      0.2-0.4    0.1-0.4    0.2-0.4
3      0.3-0.5    0.2-0.5    0.3-0.5
4      0.4-0.6    0.3-0.6    0.4-0.6
5      0.5-0.7    0.4-0.7    0.5-0.7

Note.This what I found in Plating Standards and Specifications. Please double check.

A. Hello Rajiv!

Federal standards such as QQ-Z-325 are maintained by the General Services Administration, a part of the US Government. They chose to cancel this one back in March of 1982. While they did not supersede the specification, they did mention in the cancellation notice that ASTM has a fine document numbered ASTM B633 [affil link] that people can use for acquisition.

That specification correlates the thickness of the coating to the service that the part is expected to take. There is no simple "Class 1". So, I expect you'll have to ask your customer what thickness they want.