PURPOSE: A method for forming a chromate coating for tin coating steel sheet with excellent paint adherence with no addition of specific elements is provided. CONSTITUTION: The method is characterized in that a chromate solution having a sodium dichromate concentration of 20 to 30g/L is electro-coated on the surface of tin plate in an amount of 3.0 to 4.0 C/dm¬2. In the method, the chromate solution has a temperature range of 46 to 55°C, and a pH range of 4.0 to 5.0.

A method for forming chromate coating for tin coating steel sheet with excellent paint adherence

PURPOSE:To convert an alloy layer of a tin plate to structure of high rust prevention and improve the corrosion resistance of the thinly coated tin plate by plating tin on a nickel plated steel plate prior to annealing and further subjecting the same to a chromate treatment then to a tin melting treatment. CONSTITUTION:After a steel plate made by cold-rolling of an ingot material or the like to about 0.15-0.33mm. thicknesses is degreased, it is subjected to nickel plating of 0.02-0.2g/m by using a watt bath or the like then to annealing at about 550-720 deg.C after rinsing and drying; thereafter, this is subjected to skin pass rolling then to tin plating after degreasing and pickling. A halogen bath or the like is used for the tin plating, and the stuck amount of tin is limited to 0.05-1.5g/m , so that the chromate is buried like islands in the tin layer in the stage of reflowing and the iron-tin alloy is made finer. The steel plate tin-plated in this way is chromated in an aq. sodium dichromate soln. at 0.3- 10Coulomb/dm quantities of electricity, after which it is subjected to a tin melting treatment then to sealing by a chemical treatment.

Production of surface treated steel plate of high rust prevention for welded can

PURPOSE:To produce a thinly coated tin plate of superior rust resistance and corrosion resistace by subjecting a cold-rolled steel plate which is degreased and pickled to thin plating and further to ca chromate treatment followed by a tin melting treatment and a sealing treatment. CONSTITUTION:A steel plate which is subjected to cold rolling to about 0.15- 0.33mm. then to annealing, skin pass rolling, degreasing and pickling is plated with tin by using a halogen bath or a borofluoride bath, whereby it is stuck with 0.05-1.5g/m tin and a dense alloy layer having no pinholes is formed. This tin-plated steel plate is chromated at 0.3-10Coulomb/dm quantities of electricity in an about 30g/laq. sodium dichromate soln. (about 40-60 deg.C), whereby it is improved of rust resistance. Following to this, this is subjected to a tin melting treatment and after it is rinsed and dried, it is subjected to sealing by a cathodic treatment of about 4.5 Coulomb/dm quantities of electricity in an about 30g/ l aq. dichromate acid soln. (about 40-60 deg.C soln. temps.).

Production of surface treated steel plate for seam welded can

PURPOSE:To improve the paint adhesiveness of an electrolytic tin plate in the stage of producing the electrolytic tin plate by tin plating of a steel plate by dipping the steel plate into an aq. soln. prepd. by incorporating specific ions into an essential material consisting of soluble chromic acid salts after a reflow treatment of tin plating. CONSTITUTION:The surface of the steel plate is cleaned by degreasing and pickling and thereafter the steel plate is subjected to tin plating and further to the reflow treatment to form the electrolytic tin plate. The plate is immediately dipped into the aq. soln. which contains chromic anhydride, sodium chromate, sodium dichromate, sodium acetate and other soluble chromic acid salts as the essential material and is added with an assistant contg. either or both of an SO 4 ion source such as sulfuric acid and F-ion source such as NH4F or HF, is adjusted to 1-3pH and is kept at >=95 deg.C. The content of SnO2 on the tin surface after the reflow treatment is decreased and the amt. of the chromate film is increased. The steel plate is rinsed and dried and the electrolytic tin plate having the excellent corrosion resistance and paint adhesiveness is produced.

Post treatment of electrolytic tin plate

PROBLEM TO BE SOLVED: To impart corrosion resistance and workability to a steel sheet by having a tin coating layer of a specific range in which a (101) face is included at a specific ratio on at least one surface of the steel sheet. SOLUTION: The tin coated steel sheet having the tin coating layer of 0.3 to 12 g/m2 into which the (101) face is included at >=20%, more preferably 20 to 80% on at least the one surface of the steel sheet is prepared. The method for applying the plating is executed by applying the tin coating by electroplating from an acidic bath of, for example, sulphuric acid or phenol sulfonic acid. A tin coating quantity and the integration degree of tin crystals are controlled by properly setting a current density, plating temperature, etc. The integration degree of the tin crystals is measured by a reflection X-ray diffraction method. Further, a chromate film of 2 to 20 mg/m2 in the quantity equivalent to metal Cr is imparted to the front surface of the steel sheet by subjecting the steel sheet to an immersion treatment in a chromic acid solution containing a sodium dichromate solution or to a cathode electrolytic treatment in order to prevent the discoloration to black or yellow by the oxidation of the tin coated steel sheet.

A method for forming chromate coating for tin coating steel sheet with excellent paint adherence

References

Production of surface treated steel plate of high rust prevention for welded can

Production of surface treated steel plate for seam welded can

Post treatment of electrolytic tin plate

Sn plated steel sheet having excellent corrosion resistance and workability