Salt-spray corrosion behavior of a Cu-Al composite plate under AC current

Cu-Al composite plate corrosion tests, under a 0-100 A AC current, were conducted for 48 hr in a neutral salt spray. The morphology and corrosion products were studied by scanning electron microscope and X-ray powder diffraction, through which the effect of the current was analyzed. Meanwhile, the rate and degree of corrosion were evaluated by weight loss, electrochemical and electrolytic conductivity detection methods. The results showed that when the current increased, the corrosion rate initially increased and then decreased. When the current value was 50 A, the corrosion rate was the highest. The corrosion of the Cu-Al composite plate mainly included galvanic corrosion at the interface and pitting on the aluminum matrix, with no corrosion on the copper matrix. The state of the passivation film changed to loose, peeling, rupture, accumulation, compact, and so on when the current value increased. The type of corrosion product was not affected by the current value. The current affects the electromobility of the chloride ions by influencing the conductivity of the corrosion medium. The higher the electromobility of the chloride ions, the less the destruction of the passivation film and as a result, there is a decreased rate and degree of corrosion.