Pretreating process for vitreous enamelling

Claim 2

A VITREOUS ENAMELLING PROCESS FOR A STEEL SHEET, COMPRISING ROUGHENING THE STELL SHEET BY ELECTROLYSIS, APPLYING AN AQUEOUS SOLUTION OF WATER GLASS ON THE ROUGHENED SURFACE AND DRYING THE SOLUTION TO FORM A WATER GLASS LAYER THEREON, PRESS SHAPING THE STEEL SHEET HAVING THE WATER GLASS LAYER THEREON,PRES WASHING AWAY THE WATER GLASS LAYER WITH WATER AND APPLYING A VITREOUS ENAMEL LAYER ON THE ROUGHENED SURFACE OF THE STEEL SHEET AFTER THE WATER GLASS LAYER IS WASHED AWAY.

Claim 3

A process according to claim 1 and further comprising a step of applying a solution of a wax dissolved in an organic solvent on the water glass layer so as to form a wax coating on the water glass layer, said wax coating normally being solid phase at room temperature.

Claim 4

A vitreous enamelling process to claim 1, wherein said roughening is effected by positioning a cathode plate parallel and in close proximity to the surface of the steel sheet so that a gap is formed therebetween, injecting a liquid electrolyte under pressure and at high speed into the gap between the cathode plate and the steel sheet so that the electrolyte fills the gap while quickly passing therethrough, and applying a potential across the cathode plate and the steel sheet to cause the steel sheet to act as an anode and etch the steel sheet surface by a current flowing between he cathode plate and the steel sheet.

Claim 5

A vitreous enamelling process according to claim 3, wherein the steel sheet is continuously moved at high speed relative to the cathode plate during the etching operation, and said liquid electrolyte is recirculated through a closed loop system including a reservoir, a pressurizing pump, a nozzle means, and said gap between the cathode plate and the steel sheet, said liquid electrolyte being delivered to the nozzle means under pressure by said pressurizing pump so that the nozzle means injects the liquid electrolyte into the gap between the cathode plate and the steel sheet under pressure and at high speed.

Claim 6

A process according to claim 1, wherein said roughened surface of the steel sheet is phosphate coated before being provided with said water glass layer.

Claim 7

A process according to claim 1, wherein said roughened surface of the steel sheet is nickel plated before being provided with said water glass layer.

Claim 8

A process according to claim 1, wherein said steel sheet is continuously moved during said roughening operation relative to a stationary cathode plate positioned parallel and in close proximity thereto to form a gap therebetween, a liquid electrolyte under pressure is injected at high speed into the gap between the steel sheet and the cathode plate so that the electrolyte fills the gap while quickly passing therethrough, an anode plate is positioned parallel and in close proximity to the steel sheet to form a gap therebetween at a point different from said cathode plate, an electrically conductive liquid under pressure is injected at high speed into the gap between the anode plate and the steel sheet so that the electrolyte fills the gap while quickly passing therethrough, and applying a potential across the anode plate and the cathode plate thereby etching the surface of the steel sheet by an electric current flowing between the anode and cathode plates through the steel sheet.

Claim 9

A vitreous enamelling process according to claim 1, wherein the water contains an active amount of an alkaline compound selected From the group consisting of sodium hydroxide, sodium silicate, and sodium phosphate.

Claim 10

A vitreous enamelling process according to claim 8, wherein the water contains a surface active agent.

Claim 11

A vitreous enamelling process according to claim 1, wherein said water glass layer is about 2 to 5 micron thick.