Passivation
Passivation is the build-up of a thick, stable oxide layer on metal surfaces that prevents corrosion. This layer protects the material against chemical attack.
Physicochemical Mechanism of Action
Passivation is a process where a thin oxide layer forms on the surface of a metal. This layer is so stable and dense that it prevents direct contact with the surrounding medium. This stops the electrolytic reactions that would lead to corrosion.
Metallurgical Relevance & Risks in Welding
Passivation is especially important in the welding industry because it protects the material from corrosion damage. Missing or incomplete passivation can lead to cracks and loss of strength. It is crucial that the oxide layer is properly built up after welding.
Shop Practice & Action Steps
To ensure effective passivation, take the following steps:
• Use passivating chemicals like sulfate-based solutions after welding.
• Make sure the metal surfaces are clean and dry before passivation.
• Keep temperature and time constant during passivation to form a uniform oxide layer.