Multi-layer corrosion resistant coating for fasteners and method of making

• US 5,275,892 A
• Filed: 03/27/1992
• Issued: 01/04/1994
• Est. Priority Date: 11/05/1987
• Status: Expired due to Fees

• Current Assignee: Whyco Technologies, Inc. (Whyco Finishing Technologies LLC)
• Original Assignee: Whyco Chromium Company Incorporated
• Inventors: Hyner, Jacob, Lewis, Barbara S.
• Primary Examiner(s): Niebling, John
• Assistant Examiner(s): Leader, William T.
• Application Number:
  US07/858,567
• Time in Patent Office: 648 Days
• Field of Search: 205/176, 205/177, 428/648, 428/658, 428/659, 428/667, 428/674, 428/675, 428/679, 428/935, 427/405, 427/406, 411/902
• US Class Current: 428/648
• CPC Class Codes: C25D 5/10 Electroplating with more than one layer of the same or of different metals for bearings C25D7/10
• CPC Class Codes: C25D 5/611 Smooth layers
• CPC Class Codes: C25D 5/627 Electroplating characterised by the visual appearance of the layers, e.g. colour, brightness or mat appearance
• CPC Class Codes: Y10S 411/902 Metal core
• CPC Class Codes: Y10S 428/935 Electroplating
• CPC Class Codes: Y10T 428/12722 Next to Group VIII metal-base component
• CPC Class Codes: Y10T 428/12792 Zn-base component
• CPC Class Codes: Y10T 428/12854 Next to Co-, Fe-, or Ni-base component
• CPC Class Codes: Y10T 428/12903 Cu-base component
• CPC Class Codes: Y10T 428/1291 Next to Co-, Cu-, or Ni-base component
• CPC Class Codes: Y10T 428/12937 Co- or Ni-base component next to Fe-base component

Abstract

A corrosion resistant coating and process comprises the following layers applied in sequence over a ferrous metal substrate: a micro-throwing nickel-zinc alloy plating; a zinc-nickel alloy plating containing 5 to 30 weight percent nickel; a galvanically protective zinc metal plating; and either copper, nickel and chromium (or chromium substitute) plating layers or a chromate conversion layer. The coating is preferably used with a steel fastener such as a bolt or drill screw in combination with a washer.

Claims

1. A process for providing corrosion resistance to a ferrous metal fastener comprising the steps of:

a) applying a first layer of non-strike nickel or a nickel based alloy of at least 0.00005 in. thickness over said metal fastener;

b) applying over said first layer a second layer of a zinc based alloy having a major amount, by weight, of zinc and alloyed with nickel, cobalt, iron or combinations thereof;

c) applying over said second layer a third layer of zinc;

d) applying over said third layer a fourth layer of cooper;

e) applying over said fourth layer a fifth layer of nickel; and

f) applying over said fifth layer a sixth layer of chromium or metallic chromium substitute selected from the group consisting of a binary alloy comprising cobalt or tin, and ternary alloys of tin, cobalt and a third metal selected from the group consisting of antimony, zinc and a metal of Periodic Table Group IIIA or VIB.

2. The process of claim 1 wherein said layers in steps (a)-(f) are applied by electroplating.

3. The process of claim 2 wherein said nickel or nickel based alloy first layer (a) comprises a micro-throwing nickel-zinc alloy.

4. The process of claim 1 wherein said first layer (a) is nickel of greater than 0.0001 in. thickness.

5. The process of claim 1 wherein said first layer (a) is a nickel based alloy of greater than 0.0001 in thickness.

6. The process of claim 1 wherein said second layer (b) is a zinc based alloy containing from about 5 to 15 weight percent nickel and wherein said third layer (c) is essentially pure zinc.

7. The process of claim 1 wherein said second layer (b) is a zinc based alloy containing from about 5 to 15 weight percent nickel applied to a thickness of about 0.00020-0.00060 in. and wherein said third layer (c) is essentially pure zinc applied to a thickness of about 0.00005-0.0002 in.

8. The process of claim 7 wherein said copper layer is applied to a thickness of at least 0.0003 in., said nickel layer is applied to a thickness of at least 0.0002 in., and said chromium or chromium substitute is applied to a thickness of at least 0.00001 in. as a flash coating.

9. A process for providing corrosion resistance to a ferrous metal fastener comprising the steps of:

a) electroplating a first layer of a non-strike micro-throwing nickel based alloy of at least 0.00005 in. thickness over said fastener;

b) applying over said first layer a second layer of a zinc based alloy having a major amount, by weight, of zinc and alloyed with nickel, cobalt, iron or combinations thereof;

c) electroplating a third layer of essentially pure zinc at a thickness of about 0.00005-0.0002 in. over said second layer;

d) electroplating a fourth layer of copper at a thickness of at least 0.0003 in. over said third layer;

e) electroplating a fifth layer of nickel at a thickness of at least 0.0002 in. over said fourth layer; and

f) electroplating a sixth layer of chromium or metallic chromium substitute at a thickness of at least 0.00001 in. over said fifth layer, said metallic chromium substitute being selected from the group consisting of a binary alloy comprising cobalt or tin, and ternary alloys of tin, cobalt and a third metal selected from the group consisting of antimony, zinc and a metal of Periodic Table Group IIIA or VIB.

10. The process of claim 9 wherein said micro-throwing nickel based alloy first layer includes zinc in an amount less than one (1) weight percent.

11. The process of claim 10 wherein said second layer (b) is a zinc based alloy containing from about 5 to 10 weight percent nickel.

12. The process of claim 9 wherein said fastener comprises a bolt or drill screw in combination with a washer.

13. A corrosion resistant fastener having a ferrous metal substrate and, in sequence, the following layers over said substrate:

a) a first layer of a non-strike nickel or nickel based alloy of at least 0.00005 in. thickness;

b) a second layer of a zinc based alloy containing a major amount, by weight, of zinc and alloyed with nickel, cobalt, iron or combinations thereof;

c) a third layer of zinc;

d) a fourth layer of copper;

e) a fifth layer of nickel; and

f) a sixth layer of chromium or metallic chromium substitute, said metallic chromium substitute being selected from the group consisting of a binary alloy comprising cobalt or tin, and ternary alloys of tin, cobalt and a third metal selected from the group consisting of antimony, zinc and a metal of Periodic Table Group IIIA or VIB.

14. The fastener of claim 13 wherein said nickel or nickel based alloy first layer (a) comprises a micro-throwing nickel-zinc alloy which includes zinc in an amount less than three (3) weight percent.

15. The fastener of claim 13 wherein said metal fastener comprises a bolt or drill screw in combination with a washer.

16. The fastener of claim 13 wherein said second layer is a zinc based alloy containing from about 5 to 15 weight percent nickel.

17. The fastener of claim 13 wherein said second layer is a zinc based alloy containing from about 5 to 15 weight percent nickel having a thickness of about 0.00020-0.00060 in. and wherein said third layer (c) is essentially pure zinc having a thickness of about 0.00005-0.0002 in.

18. The fastener of claim 17 wherein said copper layer has a thickness of at least 0.0003 in., said nickel layer has a thickness of at least 0.0002 in., and said chromium or chromium substitute has a thickness of at least 0.00001 in.