Cast stainless steels are chromium-containing alloys primarily classified as either corrosion-resistant or heat-resistant castings based on carbon content. These materials provide superior corrosion resistance in aqueous environments and excellent service performance at elevated temperatures due to chromium additions exceeding 11%.
Corrosion and Corrosion Properties of Stainless Steels: Part One
Stainless steels owe their corrosion resistance to a spontaneous, thin oxide film that forms on their surfaces, significantly reducing corrosion rates. Chromium is the key alloying element responsible for this passive film, typically requiring about 17% chromium for effective protection. Other elements like molybdenum, nickel, and nitrogen enhance corrosion resistance in specific environments.
Corrosion and Corrosion Properties of Stainless Steels: Part Three
Intergranular corrosion, also called intercrystalline corrosion, occurs on or adjacent to the grain boundaries of a metal. It is caused by microsegregation of impurities and alloying elements on the grain boundaries.The driving force of intergranular corrosion is the difference between the electrode potentials of the grain boundary and the grain itself, which form a galvanic cell in presence of an electrolyte.