Effect of Different Corrosion Levels on the Mechanical Behavior and Failure of Threaded Elements

This research concerns the study of corrosion effects on different threaded elements to analyse bolted joints working in a saline environment. In particular, this article examines the mechanical behavior of a M8 junction realized by different steels and subjected to different degrees of corrosion. Four materials were investigated: a low-alloyed structural steel in the original condition and the same after zinc-plating; a quenched and tempered steel; and an austenitic stainless steel. For each steel were tested a certain number of threaded rods exposed to a saline water solution, simulating the atmospheric exposure to an aggressive environment. The samples were characterized by different intervals of exposure. During these periods, the threaded elements (threaded rods) were kept in tension applying a tightening torque proportional to the yield strength of the tested steel, to evaluate their susceptibility to stress corrosion cracking. Before and after the different corrosion steps, some metallographic analyses, static tensile and fatigue tests, were carried out to determine, for each sample, the degree of corrosion and its influence on the reduction of the junction resistance. In order to evaluate the stress-intensifying factor and its variation with the imposed degree of corrosion was carried out a FEM analysis