NCARB Project Development and Documentation (PDD) Practice Exam

Ocean spray acts as an electrolyte because it contains salt and moisture that allow ions to move between metals in contact. When carbon steel and aluminum are joined and exposed to this electrolyte, a galvanic cell forms: electrons flow from the more anodic metal to the more cathodic metal. The anodic metal corrodes faster while the other metal is protected, so the spray drives galvanic corrosion between the two dissimilar metals. The other options don’t fit: the spray doesn’t selectively create a protective oxide on aluminum in this setup, it doesn’t neutralize corrosion on carbon steel, and painting doesn’t guarantee complete prevention of galvanic action if the coating is breached.