Metal treatment – Compositions – Heat treating
Patent
1985-05-07
1987-04-14
Silverberg, Sam
Metal treatment
Compositions
Heat treating
148 615Z, C23C 2212
Patent
active
046576002
ABSTRACT:
A method of forming a chemical phosphate coating on the surface of steel with a treatment bath made without directly adding any oxidizing agent such as nitrite ions or hydrogen peroxide, and maintaining its temperature in a range not exceeding 40.degree. C., its pH in the range of 2.5 to 4.5 and its oxidation-reduction potential (ORP in terms of the normal hydrogen electrode potential) in the range of 150 to 550 mV. The bath is formed from an aqueous solution of the two components, i.e. the first component, an acidic solution consisting mainly of oxo acid ions, such as, NO.sub.3.sup.-, phosphoric ions (H.sub.3 PO.sub.4 or H.sub.2 PO.sub.4.sup.-), and metal ions, such as Zn.sup.2+, and the second component, an alkaline solution containing hydroxide ions (OH.sup.-). Preferably, the bath has a temperature of 20.degree. C. to 30.degree. C., a pH value of 3.0 to 4.0 and an ORP of 350 to 450 mV.
REFERENCES:
patent: 4113519 (1978-09-01), Oka et al.
patent: 4180417 (1979-12-01), Oka et al.
patent: 4565585 (1986-01-01), Matsuda
Nippondenso Co. Ltd.
Silverberg Sam
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