Summary for qq-z-325 zinc plating Discussion
Zinc plating specification QQ-Z-325 is the focus of this thread, with Mallesh Gowda asking whether the old federal spec can still be supplied and what the ASTM equivalent is for “ZINC PLATE QQ-Z-325, CLASS 1.” In the earlier related question, Rajiv Maheshwari asked whether QQ-Z-325 Type II Class I yellow zinc plating defined thickness in microns. Harshad Vyas reported finding QQ-Z-325C thicknesses of 25 µm, 13 µm, and 5 µm for different classifications, but advised double-checking. The clearest guidance came from the answer noting that QQ-Z-325 was canceled by the U.S. General Services Administration in March 1982; it was not formally superseded, but the cancellation notice pointed users to ASTM B633 for procurement. That answer also cautioned that ASTM B633 ties coating thickness to service conditions and does not map neatly to a simple “Class 1,” so the customer must specify the required thickness.
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Q. Dear Sir,
From the web search I come to know that QQ-Z-325 is superseded by ASTM B633
Is still supplier able to produce this spec?
If not what is equivalent spec for ‘ZINC PLATE QQ-Z-325, CLASS 1’ in ASTM standard.
Mallesh Gowda
– Bangalore Karnataka
September 15, 2023
⇩ Similar, related, Q&As — oldest first ⇩
Q. Dear sir,
I have been asked to zinc plate a cold rolled steel sheet fabricated part according to Zinc plating standard QQ-Z-325 Type II Class I, colour Yellow. Does this standard explain the thickness in micron, if so please inform.
Rajiv maheshwari
manufacturers of Steel fabricated components – Aligarh, U.P., India
2004
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.
Harshad vyas
– Alhambra California
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 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.
Lee Gearhart
metallurgist – E. Aurora, New York