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JIS G3312

The JIS G3312 document defines requirements for making prepainted steel sheets and coils. This industrial standard guides the production of the product in Japan.

What is the JIS G3312?

JIS G3312 refers to the industrial standard for flat steel products. Japanese manufacturers must follow the conditions and specs listed in the document. It also explains the requirements for shape, dimensions, and surface treatment. It also includes prescribed testing methods.

This document serves as the English translation of the Japanese document. This is from the Japan Iron and Steel Federation (JISF) and follows existing laws. Steel manufacturers in the Asian nation follow the standards outlined in the document.

Classifications of Paint Coatings

Paint coatings for prepainted flat steel products fall into three classes. This comes from test results done on paint coating durability. Makers test both sides of the steel sheet. The different classes are as follows:

  • Class 1 refers to a single coat that meets Clause 5 specifications.
  • Class 2 are products with a double coating that meets Clause 5 specifications.
  • Class 3 are products with two or more coats meeting Clause 5 specifications.

Clause 5 of the JIS G3312 refers to paint coating durability. Tested products should show no defects, aside from slight rust and blisters. The coating should protect the steel product from cracks and peeling. Chalking and fading criteria vary upon agreement.


Japanese steelmakers must abide by the JIS G3312. In doing so, they ensure the quality of the products they deliver.

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