Investigation into the Mitigation of Crevice Corrosion of Aluminum–Copper Contacts in Seawater by Regulating the Contact Surface Roughness

Crevice corrosion for dissimilar metal contacts is a key problem in engineering applications. This work has attempted to prevent the ingress of corrosive media into the crevice between aluminum alloy and copper by controlling the roughness (machining accuracy) of the contact surfaces. Both electrochemical and alternating dry/wet immersion tests were used to investigate the corrosion resistance of aluminum alloy–copper contacts with different contact surface roughness. Considering the relationship between the contact surface roughness and the liquid–solid contact angle and the crevice width, a finite element model based on fluid dynamics theory is established to analyze the effect of the contact surface roughness on the seawater infiltration depth in the contact crevice. The distribution of corrosion products on the aluminum alloy and copper surfaces is observed by optical microscope and scanning electron microscope. The phase composition of the corrosion products is analyzed by X-ray diffraction technique. The results show that the corrosion resistance of the contact improves as the roughness of the contact surface decreases. This is attributed to the fact that the infiltration of seawater is retarded due to the decrease in the crevice width and increase in the contact angle with the decrease in the contact surface roughness.