초록 ▼

A process for forming a zinc phosphate coating on an aluminum substrate is provided to obtain good coverage by the coating. The coating preferably has a columnar or nodular crystal morphology and a coating weight of at least about 150 mg/ft.sup.2. The aluminum substrate is contacted with a zinc phos

A process for forming a zinc phosphate coating on an aluminum substrate is provided to obtain good coverage by the coating. The coating preferably has a columnar or nodular crystal morphology and a coating weight of at least about 150 mg/ft.sup.2. The aluminum substrate is contacted with a zinc phosphate conversion coating bath which contains: (a) from about 0.4 to 2.5 g/l zinc ion; (b) from about 5 to 26 g/l phosphate ion; (c) from about 0.4 to 1.5 g/l fluoride ion; (d) from about 4 to 400 mg/l ferrous ion; and (e) from about 0.01 to 2 g/l ammonium ion. The zinc phosphate conversion coating is formable on an aluminum substrate in the presence or absence of an accelerator. Also provided is an aqueous zinc phosphate conversion coating concentrate which contains: (a) from about 10 to 60 g/l zinc ion; (b) from about 160 to 400 g/l phosphate ion; (c) from about 2 to 40 g/l fluoride ion; (d) from about 0.2 to 2.0 g/l ferrous ion; and (e) from about 1.0 to 25 g/l ammonium ion. The concentrate may be diluted with an aqueous medium in a weight ratio of about 1:10 to 1:100 to yield a zinc phosphate conversion coating bath.

대표청구항 ▼

[ I claim:] [1.] A process for forming a zinc phosphate coating having a coating weight of at least about 150 milligrams/foot.sup.2 (1612 milligrams/meter.sup.2) on an aluminum substrate, comprising contacting said aluminum substrate with a zinc phosphate conversion coating bath which contains: (a)

[ I claim:] [1.] A process for forming a zinc phosphate coating having a coating weight of at least about 150 milligrams/foot.sup.2 (1612 milligrams/meter.sup.2) on an aluminum substrate, comprising contacting said aluminum substrate with a zinc phosphate conversion coating bath which contains: (a) from about 0.4 to 2.5 g/l zinc ion; (b) from about 5 to 26 g/l phosphate ion; (c) from about 0.4 to 1.5 g/l of fluoride ion; (d) from about 4 to 400 mg/l ferrous ion; and (e) from about 0.01 to 2 g/l ammonium ion, wherein fluoride ion is provided from ammonium bifluoride which also acts as a source of ammonium ions and wherein said zinc phosphate coating is formed on the aluminum substrate optionally in the presence of an accelerator.