What is the outstanding corrosion characteristic of Monel Alloy that other nickel alloys lack?

Monel Alloy’s most unique merit is its superior inertness to hydrofluoric acid and all fluoride solutions, which almost all stainless steel, Inconel and Hastelloy alloys cannot withstand. Its nickel-copper matrix forms a stable protective film when contacting HF, preventing continuous substrate dissolution. It also resists atmospheric salt fog, fresh water, seawater and concentrated alkaline liquids steadily. However, it is vulnerable to strong oxidizing acids such as nitric acid, so it cannot be used in mixed acid environments containing oxidizing corrosive components.