Metal treatment – Process of modifying or maintaining internal physical... – Processes of coating utilizing a reactive composition which...
Patent
1995-04-27
1996-05-14
Silverberg, Sam
Metal treatment
Process of modifying or maintaining internal physical...
Processes of coating utilizing a reactive composition which...
C23C 2212
Patent
active
055163726
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to a process for phosphating steel strip electrolytically galvanized on one side to form nickel-containing zinc phosphate coatings on the galvanized surface. The zinc phosphate coatings are applied by brief spraying with or immersion in aqueous acidic phosphating solutions.
RELATED ART
Processes for phosphating surfaces of iron, steel, zinc and alloys thereof and also aluminium have long been known (Ullmann's Encyklopadie der technischen Chemie, 4th Edition, Vol. 15, pages 686 and 687). The object of phosphating the surfaces in question is to increase the adhesion of paint coatings and to improve protection against corrosion.
DE-A-32 45 411 describes a process for phosphating electrolytically galvanized metal articles, more particularly electrolytically galvanized steel strip, by brief treatment with acidic phosphating solutions which, besides zinc and phosphate ions, may contain other metal cations and/or anions of oxygen-containing acids with an accelerating effect. Zinc phosphate coatings with a weight per unit area of less than 2 gm.sup.-2 are formed in this process. The acidic phosphating solutions used have a content of Zn.sup.2+ cations of around 1 to 2.5 g/l and a free acid content of 0.8 to 3 points, the acid ratio of total acid to free acid being kept in the range from 5 to 10. The treatment is said to last not much longer than 5 seconds. Nitrate-containing phosphating baths are preferably used, the ratio by weight of Zn.sup.2+ to NO.sub.3- being in the range from 1:1 to 1:8 and the ratio by weight of PO.sub.4.sup.3- to NO.sub.3- being in the range from 1:0.1 to 1:2.5.
EP-A-0 219 779 describes a process for phosphating electrolytically galvanized metal articles, preferably electrolytically galvanized steel articles, more particularly electrically galvanized steel strip, by brief treatment for not much longer than 5 seconds with acidic phosphating solutions which, besides zinc, manganese and phosphate ions, may contain other metal cations and/or anions of oxygen-containing acids with an accelerating effect. To produce coatings consisting predominantly of zinc phosphate with a weight per unit area of less than 2 gm.sup.-2, the phosphating solutions used have a content of zinc cations (Zn.sup.2+) of 0.1 to 0.8 g/l, a content of manganese cations (Mn.sup.2+) of 0.5 to 2.0 g/l and a free acid content of 4 to 8 points for an acid ratio (total acid to free acid) of 2.5 to 5.
JP-A-62 020 879 describes a process for phosphating galvanized steel strip on one side. In this process, phosphating is carried out by spraying of the phosphating solution onto the underneath of the steel strip while compressed air is blown onto the upper surface of the steel strip.
Now, the problem addressed by the present invention was to produce zinc phosphate coatings by spray or dip application to steel strip electrolytically galvanized on one side in such a way that, even after phosphating, the steel side would still represent a metallically bright surface. According to the invention, this would be done in treatment times of 2 to 20 seconds without any deterioration in corrosion protection and of course in such a way that dense, compact phosphate coatings would be formed on the galvanized side in the treatment times mentioned and in such a way that satisfactory forming properties would be obtained.
A further problem addressed by the invention was to apply the phosphate coatings thinly with weights per unit area of 0.5 to 3.0 gm.sup.-2 and, more particularly, in the range from 1.0 to 2.0 gm.sup.-2 without at the same time having to sacrifice uniform coverage of the steel strip galvanized on one side with a finely crystalline, firmly adhering and compact zinc phosphate coating.
In the context of the invention, the expression "steel strip electrolytically galvanized on one side" is of course also intended to encompass generally known zinc alloys (for example ZNE-electrolytically applied zinc alloy containing 10 to 13% of Ni or ZFE-electrolytically applied, Fe-containing zinc alloy
REFERENCES:
patent: 4793867 (1988-12-01), Charles et al.
Ullmann's Encyklopadie der technischen Chemie, 4th Edition, vol. 15, pp. 686 and 687.
"Uberwachung von Phosphatierungsbadern (Monitoring of Phosphating Baths)", Galvanotechnik, 59 (1968), No. 1, pp. 37-39 (Eugen G. Leuze-Verlag, Saulgau).
Geruhn Dieter
Mady Raschad
Panter Frank
Peters Hubertus
Ricke Franz
Henkel Kommanditgesellschaft auf Aktien
Jaeschke Wayne C.
Krupp Hoesch Stahl AG
Ortiz Daniel S.
Silverberg Sam
LandOfFree
Process for phosphating steel strip galvanized on one side does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for phosphating steel strip galvanized on one side, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for phosphating steel strip galvanized on one side will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1893211