Investigation of corrosion behaviour of hydrogenated 7075-T6 aluminum alloy

The corrosion behaviour of high strength aluminium alloy type 7075-T6 precharged with hydrogen for various charging times was investigated using electrochemical polarization and free corrosion potentials measurement techniques. The results showed that the precharged 7075-T6 aluminium alloy with hydrogen exhibited lower open-circuit (OCP) and breakdown potentials in deaerated 0.5 M NaCl than those for the non-hydrogenated material. Moreover, the OCP and breakdown potentials decreased with increasing the precharging time. Microscopic observations of the exposed surfaces revealed that intergranular attack was formed in non-hydrogenated specimens whereas mixed mode of attack (i.e. intergranular and transgranular) were formed in the precharged ones during potentiostatic polarization. Moreover, the pits formed during the free corrosion potential testing were observed to be larger on the exposed surfaces of hydrogen precharged specimens. The severity of attack and pitting was observed to increase with increasing the precharging time. Consequently, the corrosion resistance of hydrogen precharged of 7075-T6 aluminium alloy with hydrogen was lower than that for non-hydrogenated material.