Preventing Galvanic Corrosion

Preventing Galvanic

Galvanic corrosion occurs when two dissimilar materials come into contact with each other. There are several ways of reducing and preventing this form of corrosion. Insulate the two metals from each other. If they are not in contact, no galvanic coupling will occur. This can be achieved by using non-conductive materials between metals APAC can supply nylon washers if dissimilar metals come into contact. A sleeve can also be used to isolate the two dissimilar materials.

Towers can also be earthed to a common ground or onto ground stakes driven 1m into the surrounding soil. To ensure there is no contact with the dissimilar materials. This can be done by using water-repellent compounds such as greases, or by coating the metals with an impermeable protective layer, such as a suitable paint, varnish, or plastic. If it is not possible to coat both, the coating should be applied to the more noble, the material with higher potential. This is advisable because if the coating is applied only on the more active material, in case of damage to the coating there will be a large cathode area and a very small anode area, and for the exposed anodic area the corrosion rate will be correspondingly high.

Using antioxidant paste is beneficial for preventing corrosion between copper and aluminium electrical connections. The paste consists of a lower nobility metal than aluminium or copper. Choose metals that have similar electropotentials. The more closely matched the individual potentials, the lesser the potential difference and hence the lesser the galvanic current. Using the same metal for all construction is the easiest way of matching potentials. Electroplating or other plating can also help. This tends to use more noble metals that resist corrosion better. Chrome, nickel, silver and gold can all be used.

Galvanising with zinc protects the steel base metal by sacrificial anodic action. Cathodic protection uses one or more sacrificial anodes made of a metal which is more active than the protected metal. Alloys of metals commonly used for sacrificial anodes include zinc, magnesium, and aluminium. This approach is commonplace in water heaters and many buried or immersed metallic structures.