Evaluating the Electrochemical Properties in the Protection Potential of Material for Use in Al Vessels in Seawater

Abstract

FRP (fiber-reinforced polymer) ships used with small boats for fishing pose numerous problems related to both the environment and recycling. From this perspective, aluminum offers an environmentally friendly substitute for FRP that is easy to recycle and imparts a high added value to fishing boats, with a reduction in fuel demands. The current density of 7075 Al alloy increases linearly with an increase in potential during anodic polarization, which implies that no passivation of this alloy occurs. With 1050 and 5456 alloys, passive films form during anodic polarization but are destroyed by the Cl in seawater, only to regrow as a result of the self-healing capacity of aluminum. A shift to more anodic or cathodic conditions in the potential range of –1.5 ~ –0.68 V resulted in a sudden increase in current density. Current densities in the high-strength 7075 Al alloy showed the greatest values. In contrast, the current densities of 5456 alloy, known to have excellent corrosion resistance in seawater, were the lowest in the range of –0.70 ~ –1.3 V, and we conclude that this potential range offers optimal protection.