Selective leaching
Selective corrosion: Only certain alloy components corrode while others remain unaffected. Changes the structure and impairs mechanical properties.
Physicochemical Mechanism of Action
Selective corrosion happens when different metal components in a material have different driving potentials. The component with the lower potential corrodes faster than the other. This causes local changes in the structure and can lead to unevenness in the chemical composition.
Metallurgical Relevance & Welding Risks
Selective corrosion can show up when deoxidation is missing or insufficient during welding. It causes local changes in the structure, which hurts mechanical properties like strength and toughness. This can lead to cracks, hot cracks or other mechanical defects in the weld.
Workshop Practice & Instructions
To avoid selective corrosion, careful deoxidation is essential. Use high-quality shielding agents and make sure the weld stays protected during the cooling pass. For special alloys it can help to run the welding process in a closed system or to add corrosion inhibitors.