Copper has been a fundamental element to mankind for many thousands of years, with widespread use in construction, piping and cooking utensils. Along with excellent thermal (and electrical) conductivity, it resists corrosion and fouling in marine environments.
As an addition to Ferralium it significantly increases pitting corrosion resistance. It is believed to heighten the passivating properties of molybdenum and reacts with absorbed sulphides on the surface, forming an insoluble copper sulphide ‘protective layer’ that stifles ongoing corrosion that occurs near inclusions and other breaks in the passive film of this stainless steel. As such, it helps to achieve superior resistance in seawater and many acids such as sulphuric, nitric and phosphoric acid.
The benefit of copper is recognised elsewhere. For instance, Hastelloy® C2000 stands apart from other nickel alloys for its deliberate addition of copper to enhance resistance to sulphuric acid. Despite this recognition, Ferralium remains unique amongst stainless steels for its high level of copper addition, contributing to its superior performance; it contains almost 2.0% copper, whereas S32750 contains no more than 0.5% copper and S32760 no more than 1.0% copper.