CSA Welded Steel Construction – Metal Arc Welding (W59) Welding Inspector Level 1 Practice Test 2026 - Free Welding Inspector Practice Questions and Study Guide

Diffusible hydrogen content is the amount of hydrogen that can diffuse out of the weld metal and potentially cause hydrogen-induced cracking. To compare this consistently for welds of different sizes, it is expressed as a volume of hydrogen per a fixed mass of weld metal. The standard unit is milliliters of hydrogen per 100 grams of weld metal. This mass-based normalization makes it practical for specifying and evaluating hydrogen content across electrodes and welds, especially for quenched and tempered steels where low diffusible hydrogen is critical. Other units would complicate comparisons or aren’t the convention used in welding specifications, so the correct unit is ml per 100 g of weld metal.