Galvanic corrosion
Contact corrosion occurs when two metals with different electrochemical potentials come into contact and a conductive electrolyte is present. This leads to an electrochemical reaction that wears away the surface material.
Physical-Chemical Mechanism of Action
Two metals with different electrochemical potentials form a galvanic cell. When they are connected by a conductive electrolyte, current flows between the metals. The metal with the lower potential (cathode) wears away, while the metal with the higher potential (anode) receives electrons.
Metallurgical Relevance & Risks in Welding
Contact corrosion can lead to a deterioration of mechanical properties and the formation of cracks. It increases resistance values at contact points, which is particularly problematic in electrical and electronic engineering.
Workshop Practice & Instructions
When welding metals with different potentials, use a suitable protective layer or barrier material to prevent contact between the metals. Ensure that all metals are cleaned before welding and that no fine particles or impurities are present.