Method and agent for passivating iron and steel surfaces

摘要: The metal surfaces are treated with 0.5 to 5 wt. % aqueous solutions (pH value 7.5 10.5), in which is contained a synergistic combination--giving clear solution water--of corrosion-inhibiting substances. combination consists of: a. one or more maleic acid mono-n- -iso-alkylamides 6 14, preferably 8 10 C atoms, b. alkalolamines, mono-, di- and/or tri-ethanolamine, and c. complexing phosphonic acids, 1-hydroxy-alkyl-1,1-diphosphonic acid, 1-aminoalkyl-1,1-diphosphonic phosphonocarboxylic of the formula: ##STR1## Preferred acids 1-hydroxyethane-1,1-diphosphonic 2-phosphonobutane-1,2,4-tricarboxylic nitrilotrimethylene-phosphonic acid. weight ratio a:b should be 1:0.3 1:10, that a:c, 1:0.01 1:0.5. can contain additionally surfactants, non-ionogenic surfactants small quantities, also builders, phosphates borates.