Influence of hot-dip galvanization on the fatigue performance of high-strength bolted connections

In the present work, the influence of hot-dip galvanization (HDG) on the fatigue behaviour of high-strength bolted details is investigated through a set of 15 constant-amplitude tests. Cyclic behaviour of coated specimens is hence compared against results for unprotected samples drawn from literature, i.e., both with reference to neutral and aggressive exposure conditions. Namely, while behaviour of coated samples is moderately inferior as respect to uncoated ones in dry air (–6 % in terms of characteristic fatigue strength, probability of failure P_F = 5 %, confidence interval CI = 75 %), their performance still complies with European normative requirements for double covered joints, and galvanization proves to be highly effective when corrosion is likely to occur (with a characteristic strength increase of [+12 %; +52 %]). Finally, fractography analyses on both uncoated and coated specimens were performed, suggesting that hydrogen embrittlement may play a role in reducing fatigue strength of coated joints, that is, especially within the high-cycle fatigue regime.