| 摘要 |
PURPOSE:To provide a surface preparing soln. for iron and steel which has the excellent corrosion and heat resistance as a film and the stability of the soln. by incorporating a water-soluble poly(meth)acrylic acid having a specific weight average mol.wt., a water-soluble Cr compd. having a limited content of Cr<6+> and having prescribed property, and an orthophosphoric acid respectively at prescribed ratios. CONSTITUTION:A surface preparing soln. for iron and steel is formed by contg. 0.05-5wt% water-soluble poly(meth)acrylic acid (component A) having 2,000- 15,000 weight average mol.wt., 0.1-50wt% (in terms of Cr2O3) a water soluble Cr compd. (component B) which itself is volatile, and is a reducing agent forming water or gas hardly soluble in water when oxidized, is formed by reducing partially Cr2O3 and in which the content of Cr<6+> is 50-80wt% of the total content of Cr, and 0.1-1.5wt% orthophosphoric acid. The weight ratio of the above- described component B to the component A must be 2-10. Such surface preparing soln. is applied by a method such as dipping, spraying or brushing on iron and steel products having cleaned and dried surfaces. As a result, the corrosion resistance of the iron and steel products is improved by >=2 times as compared to the case when the conventional surface preparing soln. is used. |
