| (19) |
 |
|
(11) |
EP 0 363 200 A3 |
| (12) |
EUROPEAN PATENT APPLICATION |
| (88) |
Date of publication A3: |
|
18.07.1990 Bulletin 1990/29 |
| (43) |
Date of publication A2: |
|
11.04.1990 Bulletin 1990/15 |
| (22) |
Date of filing: 05.10.1989 |
|
| (51) |
International Patent Classification (IPC)5: C23C 22/23 |
|
| (84) |
Designated Contracting States: |
|
DE FR GB |
| (30) |
Priority: |
06.10.1988 JP 252435/88
|
| (71) |
Applicant: NIPPON PAINT CO., LTD. |
|
Osaka-shi
Osaka 530 (JP) |
|
| (72) |
Inventors: |
|
- Kiyosawa, Susumu
Hirakata-shi
Osaka (JP)
- Wada, Yutaka
Sakai-shi
Osaka (JP)
- Hosomi, Masaki
Kobe-shi
Hyogo (JP)
|
| (74) |
Representative: Stuart, Ian Alexander et al |
|
MEWBURN ELLIS
York House
23 Kingsway
London WC2B 6HP
London WC2B 6HP (GB) |
|
| |
|
| (54) |
Improvement of zinc phosphate treatment for cold working |
(57) The present invention provides a zinc phosphating method for cold working which hardly
produces sludge and can be carried out in a short period of time. The method comprises
treating a steel material with a surface conditioning solution comprising 1 to 20
ppm of titanium ion and having a pH of 8 to 11, and then treating it with a chemical
solution comprising zinc ion in a concentration of 1 to 20 g/l, phosphate ion in a
concentration of at least 5 g/l, nitrate ion in a concentration sufficient to have
a concentration ratio of phosphate ion / nitrate ion of at least 1/3, pyrophosphate
or tripolyphosphate ion in a concentration of 0.2 to 2 g/l, Fe (II) ion in a concentration
of 0.1 to 20 g/l and a material decomposing nitrite ion and not oxidizing the Fe (II)
ion in a concentration of at least 0.05 g/l.