NSK has developed ES1, an excellent stainless bearing steel with superior corrosion resistance for use in high-humidity, chemical and hygienic environments. This new steel protects rolling bearings against corrosion and rolling contact fatigue, prevents cracks due to rolling contact stress and increases their long term operating life. ES1 steel has no eutectic carbides, but consists of fine carbides, nitrides and strong martensite. It also has optimum nitrogen content and lower carbon content to suppress the eutectic carbides generated in conventional steelmaking process. The operating benefits of this new material specification have been proven following extensive testing by NSK. ES1 outperformed other stainless steels in a 5% aqueous sodium chloride immersion test, a salt-water spray test, 5-N sulphuric acid and 5-N hydrochloride solution immersion tests and during life tests in water.