To prevent galvanic corrosion between dissimilar metals in long-term storage, what specific non-dielectric barrier application method is critical when intermixing fasteners and small components from different alloys?

Galvanic corrosion occurs when two electrochemically dissimilar metals are in electrical contact and exposed to an electrolyte, such as moisture. One metal, termed the anode, which is more active or less noble in the galvanic series, corrodes preferentially, while the other metal, the cathode, which is less active or more noble, is protected. To prevent this phenomenon when intermixing fasteners and small components from different alloys for long-term storage, the critical non-dielectric barrier application method is sacrificial metallic plating. This process involves applying a thin, uniform layer of a metal that is electrochemically more active, meaning less noble, than both the fastener's base material and the component it will be mated with. Common examples of such plating metals include zinc, cadmium, or aluminum. This metallic plating acts as a non-dielectric barrier in two critical ways. First, it provides a physical separation, preventing direct metal-to-metal contact between the primary dissimilar alloys. Second, and most importantly for a non-dielectric barrier, it offers sacrificial protection. Should the plating be compromised, or if an electrolyte bridges the plated fastener and the mating component, an electrochemical cell forms. The plating material, being more anodic than both the fastener's substrate and the other dissimilar component, becomes the anode and corrodes preferentially. This intentional consumption of the plating material protects both the underlying fastener material and the other dissimilar alloy component from corrosive attack. For example, a steel fastener that is zinc-plated, when connected to an aluminum component in the presence of moisture, will experience the zinc layer corroding first. The zinc, being more anodic than both steel and aluminum, actively sacrifices itself, thereby preserving the integrity of both the steel fastener and the aluminum component. This method is essential for long-term storage as it actively mitigates potential corrosion pathways even when direct physical contact is possible or when environmental moisture is present, providing continuous protection by sacrificing the applied coating instead of the critical structural materials.