A micromechanical model of the cracking failure on structural steel components during hot-dip galvanizing

This paper describes a model that explains the failure during hot-dip galvanizing of structural steel components. This is an occasional problem found by galvanizers, which involves a high level of structural responsibility, and it has been considered as a stress corrosion cracking process by all experts. Considering this statement as a starting point, a complete experimental characterization of each step of the galvanizing process and its effect on the failure has been performed. The results of these tests are used to elaborate a complete model of micromechanisms which explains and describes step by step the cracking process up to failure during galvanizing. Two cases were considered, depending on whether the Sn content in the galvanizing bath was lower than 0.5% Sn or more than 0.5% Sn. Besides, two mechanical conditions are necessary to maintain the cracking process, which are: 1.- The stress intensity factor KI should be higher than a threshold value, KIscc.2.- The stress intensity factor KI should increase during all the immersion in liquid Zn.These mechanical conditions were used to formulate additional recommendations to prevent cracking failure during galvanizing.