ND steel, also known as 09CrCuSb steel, is a type of low - alloy high - strength steel that is specifically designed to have excellent corrosion resistance, especially in sulfur - containing environments.

The corrosion resistance of ND steel is mainly attributed to its chemical composition. It contains elements such as chromium (Cr), copper (Cu), and antimony (Sb). Chromium forms a passive oxide film on the surface of the steel when exposed to the atmosphere or corrosive media. This oxide film acts as a barrier, preventing further oxidation and corrosion of the underlying steel. Copper also contributes to the corrosion resistance by enhancing the stability of the passive film and promoting the formation of a protective patina. Antimony, on the other hand, improves the steel's resistance to sulfur - containing compounds, which are common corrosive agents in many industrial environments, such as in power plants burning high - sulfur coal and in oil refineries.

In power plants, ND steel is widely used in the construction of air pre - heaters. These components are constantly exposed to flue gases containing sulfur dioxide and other corrosive substances. The excellent corrosion resistance of ND steel allows the air pre - heaters to have a longer service life, reducing maintenance costs and downtime. In oil refineries, ND steel can be used in equipment that comes into contact with sulfur - rich crude oil or refined products. It can withstand the harsh corrosive conditions, ensuring the safe and efficient operation of the refinery processes.

Compared to some traditional carbon steels, ND steel offers significantly better corrosion resistance. However, its corrosion resistance can still be affected by factors such as the concentration of corrosive substances, temperature, and pH value of the environment. In highly acidic or high - temperature sulfur - rich environments, additional protective measures such as coatings or cathodic protection may be required to further enhance the corrosion resistance of ND steel - made equipment.