ABSTRACT
The degradation in fracture toughness K~c due to hydrogen embrittlement from the plating process, K,,cc-IHE, and that from environmentally induced hydrogen embrittlement, K,scc-EHE, is shown in Figure 19 for three different steels (denoted A, B, and C) for a range of platings from cadmium (Cd, or -0.85 V), through aluminum (AI) and zinc (Zn) to magnesium (Mg, or -1.25 V). Note that as the corrosion potential of the coating becomes more negative, the amount of hydrogen being generated increases, as does the amount of degradation in toughness. From the data presented in Figure 19, it can be concluded that the bolts were fabricated free of hydrogen embrittlement, K 1scc-IHE = K,c, but are susceptible to environmentally induced hydrogen embrittlement, Kbcc-EHE < K1c.
