Corrosion Prevention and Control Practice Test

When dissimilar metals are in electrical contact in a moist or salty environment, a galvanic couple forms and drives corrosion. Metals have different electrochemical potentials; in the presence of an electrolyte, electrons flow from the more anodic metal to the more cathodic metal. The anodic metal dissolves faster (corrodes) while the cathodic metal is protected. The severity grows with a larger potential difference, a small anodic area paired with a large cathodic area, higher temperature, and more conductive electrolytes. Preventing this involves insulating the metals from each other or coating them, or selecting metals with closer potentials and using barriers or sacrificial protection. The statements that say dissimilar metals prevent corrosion, cannot be in contact, or are inherently beneficial are not accurate in corrosion-prone conditions because the key risk is the galvanic current created by the potential difference.