In situ study of the deep sea electrochemical performance of aluminum-based galvanic anodes

The galvanic performance of Al-Zn-In-Mg-Ti-Ga-Mn and Al-Zn-In-Si anodes was studied in situ in the South China Sea at a depth of 1,420 m when coupled to E355DD structural carbon steel. Deep-sea field tests showed that Al-Zn-In-Mg-Ti-Ga-Mn anode surface degradation mainly occurred via uniform corrosion accompanied by some minor evidence of pitting and intergranular corrosion, whereas the Al-Zn-In-Si anode was subject to extensive intergranular corrosion. Pitting and intergranular corrosion were primary reasons for degrading the galvanic anode performance, and overall the Al-Zn-In-Mg-Ti-Ga-Mn performed better than the Al-Zn-In-Si in the deep-sea environment. There was no evidence that calcareous sediments were deposited on the protected steel surface and the protection current density in the deep sea was 72% higher than that required at the ocean surface.