Process for phosphating metal surfaces

  • US 4,944,813 A
  • Filed: 01/13/1989
  • Issued: 07/31/1990
  • Est. Priority Date: 01/14/1988
  • Status: Expired due to Fees
First Claim
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1. In a process comprising cleaning and phosphating metal surfaces, the improvement wherein the surfaces without previous activation are contacted in a temperature range of from 30°

  • C. to 70°

    C. with an aqueous solution consisting essentially of;

    (a) from about 10 to about 40 g/l of Ca2+ ions,(b) from about 10 to about 40 g/l of Zn2+ ions,(c) from about 10 to about 100 g/l of PO43- ions,(d) an accelerator selected from the group consisting of(i) about 10 to about 100 g/l of nitrate ions and(ii) about 0.1 to about 2.0 g/l of organic nitro compounds,(e) up to about 10 g/l of Ni2+ ions, and(f) up to abut 10 g/l of simple, complex, or mixed simple and complex fluoride ions,said solution having a pH value in the range from about 2.0 to about 3.8, a ratio of free acid to total acid from about 1;

    4 to 1;

    100, and a ratio by weight of Zn+2 ions to Ca+2 ions of about 1;

    0.5 to about 1;

    1.5;

    said process producing on the metal surfaces a phosphate layer containing scholzite in an areal density between about 3 and about 9 g/m2.

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