Electro-co-deposition of corrosion resistant nickel/zinc alloys onto steel substrates
First Claim
1. A process for plating a protective corrosion-resistant coating on iron or steel substrates which comprises the steps of immersing the substrates in a plating bath solution having a combined dissolved metal content consisting of nickel and zinc in the range of 10 to 25 ounces per gallon of plating bath;
- wherein the ratio of nickel to zinc in said bath is in the range of 0.1;
1 to 0.4;
1;
the nickel content of said bath is in the range 1.4 to 3.5 ounces per gallon, the balance of metal being dissolved zinc present in said plating bath solution in the range 8.4 to 21 ounces per gallon;
said bath having a pH in the range 2.3 to 4.5;
L said bath being maintained at a temperature in the range 135°
F. to 145°
F.; and
subjecting said iron substrate to a cathodic plating current density in the range 30 to 120 amperes/ft2 until the nickel/zinc alloy coated on said substrate is in the range of 0.00005 to 0.0005 inches in thickness;
said alloy having a nickel content of 10% to 15%, the balance being zinc and said coating providing a corrosion resistance to said substrate in excess of 0.5 hour per microinch of nickel/zinc alloy by the Salt Spray Test.
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Abstract
Novel plating baths and the processes for plating therewith are disclosed which provide corrosion-resistant nickel/zinc alloy coatings containing 13-15 weight/% of nickel for iron or steel substrates. The novel baths have combined nickel and zinc contents in the range of 14 to 24 ounces of metal per gallon with the ratio of nickel to zinc maintained in the range 0.1:0.4. These baths permit satisfactory plating of the alloy to be achieved at current densities in the range 30 to 120 amperes per square foot. At alloy coating thicknesses in the range 0.00005 to 0.0005 inches, a salt spray corrosion resistance in excess of 0.5 hours per microinch is afforded. Additionally, by coating the substrate, before alloy plating, with a substantially pure nickel priming layer, the corrosion resistance rate can be effectively doubled. Apparatus for the continuous plating of the priming layer and the corrosion-resistant alloy layer is also described.
22 Citations
16 Claims
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1. A process for plating a protective corrosion-resistant coating on iron or steel substrates which comprises the steps of immersing the substrates in a plating bath solution having a combined dissolved metal content consisting of nickel and zinc in the range of 10 to 25 ounces per gallon of plating bath;
- wherein the ratio of nickel to zinc in said bath is in the range of 0.1;
1 to 0.4;
1;
the nickel content of said bath is in the range 1.4 to 3.5 ounces per gallon, the balance of metal being dissolved zinc present in said plating bath solution in the range 8.4 to 21 ounces per gallon;
said bath having a pH in the range 2.3 to 4.5;
L said bath being maintained at a temperature in the range 135°
F. to 145°
F.; and
subjecting said iron substrate to a cathodic plating current density in the range 30 to 120 amperes/ft2 until the nickel/zinc alloy coated on said substrate is in the range of 0.00005 to 0.0005 inches in thickness;
said alloy having a nickel content of 10% to 15%, the balance being zinc and said coating providing a corrosion resistance to said substrate in excess of 0.5 hour per microinch of nickel/zinc alloy by the Salt Spray Test. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
- wherein the ratio of nickel to zinc in said bath is in the range of 0.1;
Specification