Galvanic corrosion
Galvanic corrosion occurs when two metals are electrically connected in an electrolyte. The less noble metal corrodes faster, and porosity leads to susceptibility to damage.
Physicochemical Mechanism of Action
Galvanic corrosion occurs when two different metals are in contact with an electrolyte. The less noble metal acts as the anode and corrodes faster, while the more noble metal acts as the cathode. Electrons flow from the less noble to the more noble metal, accelerating the oxidation of the less noble metal.
Metallurgical Relevance & Risks in Welding
Galvanic corrosion can lead to porosity and cracks. The less noble metal loses its strength and toughness, which shortens the life of the weld. This can occur especially in electrolytes like saltwater or moisture.
Workshop Practice & Instructions
To avoid galvanic corrosion, metal parts should be treated with suitable protective agents before welding. Use noble metals like silver or gold as cathode material to reduce the corrosion rate of the less noble metal. Also ensure a clean surface and avoid contact between different metals in the electrolyte.