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Zinc Plating specification QQ-Z-325

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Q. Dear Sir,
From the web search I come to know that QQ-Z-325 [Techstreet affil. link] is superseded by ASTM B633 [affil link]

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

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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 [Techstreet affil. link] 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

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 [Techstreet affil. link] 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.

lee gearhart
Lee Gearhart
metallurgist - E. Aurora, New York

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