Method for zincating aluminum articles

Abstract

Abstract A method for preparing aluminum or aluminum alloy bodies to receive an electrically deposited surface coating is disclosed. The method includes degreasing the body, if necessary, etch cleaning and zinc coating the body, washing and drying the etch cleaned and zinc-coated body, etching the dried body in 40 DEG Baume nitric acid or, when the body is an alloy of aluminum containing as much as about 2 percent of silicon, in 40 DEG Baume nitric acid which also contains from 11/2 to 3 percent of ammonium bifluoride, washing the etched body in cold running water, zincating the washed body and washing the zincated body in cold running water. The baths used in the various steps of the method of the invention and the times and temperatures used, are set forth in the following Table wherein percentages are by weight: } TEMPERA- TIME }STEP BATH TURE OF STEP }Etch cleaning Aqueous sodium hydroxide, 170-190 DEG F. 5-10 }and zinc- 1.3 to 2.7 normal, also seconds }coating containing 11/4 to 3 per- } cent of tetrasodium salt } of ethylenediamine tetra- } acetic acid and from 0.05 } to 0.15 percent of zinc } oxide }Etching - Up to about 2-5 } 110 DEG F. seconds }Zincating Aqueous sodium hydroxide, 120-160 DEG F. 1/2-5 } 21/2 to 5 normal, also seconds } containing 5 to 18 percent } of tetrasodium salt of } ethylenediamine tetra- } acetic acid and 0.4 to } 2.5 percent of zinc, } calculated as Zn }

Inventors

• 👤 Addison M. Howard

Bibliographic Details