Metallic coated steel having a siloxane film providing temporary corrosion protection and method therefor

• US 5,292,549 A
• Filed: 10/23/1992
• Issued: 03/08/1994
• Est. Priority Date: 10/23/1992
• Status: Expired due to Term

• Current Assignee: Armco Inc. (Cleveland-Cliffs Steel Holding Corp.)
• Original Assignee: Armco Inc. (Cleveland-Cliffs Steel Holding Corp.)
• Inventors: Edwards, Ricole A., van Ooij, Wim J., Sabata, Ashok
• Primary Examiner(s): Beck, Shrive
• Assistant Examiner(s): CAMERON, ERMA C
• Application Number:
  US07/965,313
• Time in Patent Office: 501 Days
• Field of Search: 427/156, 427/388.2, 427/387, 528/35, 528/38
• US Class Current: 427/156
• CPC Class Codes: B05D 7/14 to metal, e.g. car bodies involving a chemical reaction between the metal and the coating C23
• CPC Class Codes: C08G 77/04 Polysiloxanes
• CPC Class Codes: C09D 4/00 Coating compositions, e.g. paints, varnishes or lacquers, based on organic non-macromolecular compounds having at least one polymerisable carbon-to-carbon unsaturated bond ; Coating compositions, based on monomers of macromolecular compounds of groups C09D183/00 - C09D183/16
• CPC Class Codes: C09D 5/008 Temporary coatings C09D5/20 takes precedence
• CPC Class Codes: C23C 22/68 using aqueous solutions with pH between 6 and 8
• CPC Class Codes: C23C 22/74 for obtaining burned-in conversion coatings
• CPC Class Codes: C23C 2222/20 Use of solutions containing silanes

Abstract

A metallic coated steel such as a galvanized sheet is coated with a thin siloxane film having a preferred thickness of about 45 Å for providing temporary corrosion protection. The siloxane film is formed by rinsing the metallic coated sheet with an aqueous solution containing 0.5-2.0 vol. % silane and 0.1-1.0 vol. % crosslinking agent. The silane coating deposited on the rinsed sheet is cured at a temperature less than 200° C. Preferred silane and crosslinking agents are γ-aminopropyltriethoxy and (CH₃ O)₃ SiCH₂ CH₂ Si(OCH₃)₃ respectively. The siloxane film may be removed by rinsing the metallic coated steel sheet in an alkaline solution prior to coating the sheet with a phosphate conversion coating and a paint.

Claims

1. A method of providing temporary corrosion protection for steel by applying a siloxane film which is removable by alkaline rinse, comprising the steps of:

providing a steel sheet coated with a metal from the group consisting of zinc, zinc alloy, aluminum and aluminum alloy,

rinsing the sheet with a solution containing a silane and 0.1-1.0 vol. % of a crosslinking agent, and

curing the silane coating at a temperature less than 200°

C. thereby forming the siloxane film.

2. The method of claim 1 wherein the siloxane film has a thickness of 10-100 Å

.

3. The method of claim 2 wherein the siloxane film has a thickness of about 45 Å

.

4. The method of claim 1 wherein the sheet is rinsed with an aqueous solution containing the silane and the crosslinking agent.

5. The method of claim 4 wherein the solution contains 0.5-2.0 vol. % of the silane.

6. The method of claim 1 wherein the rinsing time is ≧

5 seconds.

7. The method of claim 1 wherein the crosslinking agent contains two or more Si(OH)₃ groups after being hydrolyzed.

8. The method of claim 7 wherein the crosslinking agent is (CH₃ O)₃ SiCH₂ CH₂ Si(OCH₃)₃.

9. The method of claim 1 wherein the silane is from the group consisting of amino silanes.

10. The method of claim 9 wherein the silane is γ

-aminopropyl trialkoxy.

11. A method of providing temporary white rust protection for steel, comprising the steps of:

providing a galvanized steel sheet,

rinsing the sheet in an aqueous solution containing 0.5-2.0 vol. % silane and 0.1-1.0 vol. % crosslinking agent, and

curing the silane coating at a temperature <

200°

C. thereby forming a siloxane film having a thickness of 10-100 Å

.

12. A method of providing temporary corrosion protection for steel, comprising the sequential steps of:

providing a metallic coated steel sheet,

rinsing the sheet with a silane and a crosslinking agent,

curing the silane coating at a temperature less than the decomposition temperature of the silane thereby forming a siloxane film,

removing the siloxane film by rinsing the sheet with an alkaline solution,

coating the sheet with a phosphate conversion coating, and

painting the phosphated sheet.

13. A method of providing temporary corrosion protection for steel, comprising the steps of:

providing a metallic coated steel sheet,

rinsing the sheet with a silane and a crosslinking agent,

curing the silane coating at a temperature less than the decomposition temperature of the silane thereby forming a siloxane film, and

removing the siloxane film by rinsing the sheet with an alkaline solution.

14. A method of providing temporary corrosion protection for steel by applying a siloxane film which is removable by alkaline rinse, comprising the steps of:

providing a steel sheet,

dipping the sheet into a molten bath of zinc or zinc alloy to form a galvanized sheet,

cooling the galvanized sheet to less than about 200°

C.,

rinsing the galvanized sheet with a solution containing a silane and 0.1-1.0 vol. % of a crosslinking agent whereby the silane coating is cured to the siloxane film.