In the paper reasons of damage of zinc galvanized screws M12x130 grade 12.9 were analysed. Examinations concerned analysis of fractures created as a result of screws cracking, the verification of structure correctness achieved after the heat treatment, hardness measurement at the screws cross section as well as inspections of the hydrogen content. Based on conducted examinations it was stated that the main reason of analysed screws cracking was steel hydriding - hydrogen brittleness which could take place on individual stages of the production process. Measured hydrogen content much more exceeds the acceptable values, and observed fractures are characteristic of brittle cracking.Keywords: Zinc coatings, galvanizing, hydrogen brittleness, brittle cracking
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