Corrosion behavior of 1Cr18Ni9Ti–1Cr11Ni2W2MoV galvanic couples in a simulated marine environment

The corrosion behavior of 1Cr18Ni9Ti–1Cr11Ni2W2MoV galvanic couples with different surface treatments (including chemically passivated, Cd-plated, Cu-plated, and damaged Cu-plated) was studied in a simulated marine environment. Scanning electron microscopy was used to analyze the micro-corrosion morphology and structure of the samples. Polarization curves, galvanic currents, and rates of corrosion of the samples were each measured and determined. The results showed that galvanic corrosion was much more serious on the galvanic couples than monomer corrosion. With increasing corrosion sensitivity under acidic conditions, the specimens were more prone to corrosion. Under neutral and acidic conditions, the average galvanic current densities of the damaged Cu-plated sample were five and eight times those of the Cu-plated sample, respectively, indicating that the integrity of the surface plating improved the corrosion resistance of the samples effectively. In neutral environments, the chemically passivated sample had the highest self-corrosion potential, the lowest corrosion rate, and the best corrosion resistance, while the Cd-plated sample showed the opposite behavior. The corrosion mechanism of the damaged Cu-plated and Cd-plated samples was related to the combined effects of galvanic corrosion and crevice corrosion. As the potential difference between the Cu-plated and the chemically passivated samples was less than 50 mV, the corrosion was relatively weak.