Production of multiple zinc-containing coatings

• US 4,314,893 A
• Filed: 02/19/1980
• Issued: 02/09/1982
• Est. Priority Date: 06/02/1978
• Status: Expired due to Term

• Current Assignee: OMI International Corp. (Element Solutions Inc)
• Original Assignee: Hooker Chemicals & Plastics Corp.
• Inventors: Clauss, Richard J.
• Primary Examiner(s): Kaplan, G. L.
• Application Number:
  US06/122,203
• Time in Patent Office: 721 Days
• Field of Search: 204/40, 204/41, 427/406, 428/632, 428/658, 428/659
• US Class Current: 205/148
• CPC Class Codes: C23C 28/023 only coatings of metal elements only
• CPC Class Codes: C23F 13/02 cathodic; Selection of conditions, parameters or procedures for cathodic protection, e.g. of electrical conditions
• 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: Y10T 428/12792 Zn-base component
• CPC Class Codes: Y10T 428/12799 Next to Fe-base component [e.g., galvanized]

Abstract

Markedly superior corrosion protective properties are imparted to metal-bearing surfaces at substantially reduced costs by depositing upon said surfaces one or more superimposed coatings containing zinc alloying elements located intermediate the metal-bearing surfaces and a sacrificial layer of generally pure zinc. In this manner penetration of rust inducing substances into the metal bearing surfaces is effectively precluded under substantially all environmental conditions normally encountered.

Claims

1. A method for the production of a corrosion-resistant article which comprises subjecting a metal-bearing surface of steel or iron-based alloys to electroplating in a zinc-alloy electroplating bath to form on said surface a zinc-alloy deposit which contains from about 3 to 15% of an alloying element selected from the group consisting of nickel, iron, cobalt and mixtures thereof, the remainder of said alloy being zinc, and, thereafter, electroplating on said initial zinc-alloy coating a second zinc electrodeposit in which the content of the said alloying elements is at least 1.4% less than the content of the alloying elements in the said first deposit, the remainder of said alloy being zinc.

2. The method as claimed in claim 1 wherein both the initial and second electrodeposits are produced from the same zinc-alloy electroplating bath and the amount of agitation of the bath is varied during electrodeposition to control the amount of alloying element deposited in each electrodeposited coating.

3. The method as claimed in claim 1 wherein the second electrodeposited coating is substantially pure zinc.

4. The method as claimed in claims 2, 3, or 1 wherein a chromate salt passive film is applied on top of the second electrodeposited coating.