PURPOSE: To provide a corrosion inhibitor contg. prescribed percentages of disodium hydrogenphosphite and mono- or triethanolamine and showing superior corrosion inhibiting power on different metals at the same time.

CONSTITUTION: This corrosion inhibitor contains 40W60pts.wt. disodium hydrogenphosphite and 60W40pts.wt. monoethanolamide and/or triethanolamine. The inhibitor is added to an oily substance and used, or it is used in the state of an aqueous soln. or an emulsion after adding water. To the inhibitor may be added a generally used corrosion inhibitor, a surfactant, a disinfectant, a slime controller, etc. This corrosion inhibitor is uniformly dissolved in water and shows a superior corrosion inhibiting effect on many kinds of metals.