5. Corrosion resistance

5.1 Electrochemical potential

The electrochemical voltage-pH equilibrium diagram of the molybdenum-water system at 25 C, in the absence of complexing and insoluble oxide-forming compounds, shows that molybdenum is not a noble metal (stability range below that of water). At the molybdenum-water interface, or in the presence of even small amounts of chemically active compounds, behavior can be strongly altered. Molybdenum can be passivated (protected by an oxide layer) in the presence of water or oxidizing agents such as nitric acid or ferric chloride, or by anodic passivation.

The morphology of oxides formed on molybdenum and its alloys in the presence of water at different temperatures can vary considerably, leading to better resistance at high temperatures (250...