When mass fraction of molybdenum added in nickel-molybdenum alloy exceeding 16%, the corrosion resistance of nickel-molybdenum alloy is improved significantly. This is because mass fraction of molybdenum has influence on corrosion resistance in hydrochloric acid. Improved alloy has high mass fraction of molybdenum, having good corrosion resistance in hydrochloric acid. Especially Hastelloy B has excellent corrosion resistance in boiling hydrochloric acid having different concentrations. Due to stainless steel and most of other types of metal have poor corrosion resistance in hydrochloric acid, nickel-molybdenum alloy also has poor corrosion resistance to hydrochloric acid. For this, corrosion resistance of nickel-molybdenum alloy to hydrochloric acid is more valuable. 

 

Besides hydrochloric acid, nickel-molybdenum alloy should have corrosion resistance to sulfuric acid, phosphoric acid, hydrofluoric acid, bromic acid, formic acid, acetic acid and other organic acids. The alloy also should have corrosion resistance in inoxidizable saline solutions such as aluminum chloride, magnesium chloride, copper chloride and antimony chloride or wet hydrogen chloride and other types of gas. However, nickel-molybdenum alloy has poor corrosion resistance in solutions containing oxidized ions and oxidizing acid such as nitric acid. Hydrochloric acid and sulfuric acid containing oxidizing salts (including ferric oxide, ferric sulfate and copper chloride) can increase corrosion rate of nickel-molybdenum alloy greatly. Hydrochloric acid mixed with small amount of nitric acid can exacerbate corrosion of nickel-molybdenum alloy. Dissolved oxygen in hydrochloric acid can also intensify corrosion of nickel-molybdenum alloy. For industrial valves made from nickel-molybdenum alloy, body contacting with air can enhance corrosion at entrance.   

 

Due to high nickel content, nickel-molybdenum has good corrosion resistance to chlorides. What's more, the alloy also has good corrosion resistance to most of halogen media. Nickel-molybdenum alloy also has good corrosion resistance to halide catalysts which are made of ethanediol.