Depth profiling approach to evaluate the influence of hot stamping on the local electrochemical behaviour and galvanic series of hot-dip Al-Si coating on 22MnB5 steel

Highlights: • A complex multi-layered system is formed in the Al-Si coating after hot stamping. • Hot stamping increased the overall corrosion potential of the Al-Si coating. • Si plays a crucial role on the passive electrochemical behaviour of the sublayers. • Fe enrichment influenced the passive/active electrochemical behaviour of the coating. • The active behaviour of the steel substrate was kept after hot stamping. The influence of hot-stamping process on the corrosion properties of Al-Si coating on 22MnB5 steel was locally evaluated using a depth profiling approach combining GDOES and electrochemical micro cell. The results highlight the complexity of the system and the high dependence of the local galvanic series on the hot-stamping process. Due to iron diffusion from the steel substrate into the coating, the Al-rich layers presented active behaviour, whereas the initial coating condition showed a passive behaviour. Conversely, Fe/Si-rich sublayers acted as protective barrier for the steel substrate, as they show passive behaviour with nobler corrosion potentials and lower current densities.