Passive Film Breakdown
Passive layer breakdown is the local failure of the oxide protection on metal surfaces due to chemical or mechanical action. This leads to pitting and crevice corrosion.
Physical-Chemical Mechanism of Action
The passive layer is a thin oxidized protective film on the surface of metals that protects against corrosion. When this film is destroyed by chemical destabilization (e.g., hydrochloric acid) or mechanical action (e.g., mechanical stress), local loss of protection occurs.
Metallurgical Relevance & Welding Risks
Passive layer breakdown can lead to pitting and crevice corrosion, which significantly shortens component service life. This is especially dangerous in chemically demanding environments or at high temperatures.
Workshop Practice & Action Guidelines
To avoid passive layer breakdown, metals should be thoroughly cleaned and free of chemical corrosion damage before welding. In special environments or at high temperatures, additional corrosion protection is required.