The chromium contents of the Ni-Cr-Mo alloys range from approximately 15 to 25 wt%, while their molybdenum contents range from approximately 12 to 17 wt%. The primary function of chromium is to provide passivity in oxidizing acid solutions; this is also its main function in the stainless steels. Molybdenum greatly enhances the resistance of nickel to reducing acids, in particular hydrochloric, and increases the resistance to localized attack (pitting and crevice corrosion), perhaps because these forms of attack involve the local formation of hydrochloric acid. Molybdenum provides considerable strength to the fcc solid solution because of its atomic size.