Process for anodizing aluminum materials and application members thereof

• US 5,775,892 A
• Filed: 03/22/1996
• Issued: 07/07/1998
• Est. Priority Date: 03/24/1995
• Status: Expired due to Term

• Current Assignee: Honda Giken Kogyo Kabushiki Kaisha (Honda Motor Company)
• Original Assignee: Honda Giken Kogyo Kabushiki Kaisha (Honda Motor Company)
• Inventors: Ikeda, Hideaki, Miyasaka, Hajime
• Primary Examiner(s): Gorgos, Kathryn L.
• Assistant Examiner(s): Leader, William T.
• Application Number:
  US08/621,294
• Time in Patent Office: 837 Days
• Field of Search: 205/121, 205/149, 205/153, 205/172, 205/173, 205/325, 205/332, 205/326, 205/50, 418/55.2, 123/193.2, 428/472.2, 428/667
• US Class Current: 418/55.2
• CPC Class Codes: C25D 11/06 characterised by the electrolytes used
• CPC Class Codes: C25D 5/44 Aluminium
• CPC Class Codes: Y10T 428/12854 Next to Co-, Fe-, or Ni-base component

Abstract

According to the present invention, an aluminum alloy containing silicon is anodized using an electrolyte including a compound containing an anion having complexing capability such as sodium hydrogenphosphate or tribasic sodium phosphate, a salt of an organic acid containing an oxyacid anion such as sodium citrate or sodium tartrate or an alcohol such as sorbitol, and a halide such as potassium fluoride or sodium fluoride. The use of such an electrolyte results in a reduced amount of silicon being incorporated in the anodic oxide film. When the resulting oxide film is subjected to an electrodeposition treatment such as electroplating or electrolytic coloring, wasteful consumption of electrodeposition current can be inhibited. An aluminum alloy decorative cover is produced by buffing the surface of an aluminum alloy containing silicon, forming the anodized film on the buffed surface, and subjecting the anodized film to sequential nickel and chromium plating. The anodizing process of the invention for anodizing an aluminum alloy containing silicon is used to anodize a spiral scroll member of a compressor and the inner circumferential surface of the cylinder of a cylinder block.

Claims

1. A process for anodizing an aluminum alloy containing Si, which comprises subjecting the aluminum alloy containing Si to an anodizing treatment using an electrolyte comprising:

(i) at least one compound containing an anion capable of coordinating as a ligand on a metal ion to form a complex during said anodizing treatment selected from the group consisting of sodium hvdrogenphosphate and tribasic sodium phosphate,

(ii) at least one salt of an organic acid containing an oxyacid anion selected from the group consisting of sodium citrate and sodium tartrate, or sorbitol, and

(iii) at least one halide selected from the group consisting of potassium fluoride and sodium fluoride.

2. A process for anodizing an aluminum alloy, according to claim 1, wherein the amount of sodium hydrogenphosphate, tribasic sodium phosphate, sodium citrate, sodium tartrate, sorbitol, potassium fluoride and sodium fluoride is 0.2 to 0.5 mol, 0.2 to 0.4 mol, 0.1 to 0.75 mol, 0.1 to 0.55 mol, 0.25 to 0.75 mol, 0.1 to 0.75 mol and 0.1 to 0.75 mol, respectively.

3. A process for surface treatment of an aluminum alloy containing Si, the process comprising:

a first step of subjecting the aluminum alloy containing Si to an anodizing treatment using an electrolyte comprising;

(i) at least one compound containing an anion capable of coordinating as a ligand on a metal ion to form a complex during said anodizing treatment selected from the group consisting of sodium hydrogenphosphate and tribasic sodium phosphate,

(ii) at least one salt of an organic acid containing an oxyacid anion selected from the group consisting of sodium citrate and sodium tartrate, or sorbitol, and

(iii) at least one halide selected from the group consisting of potassium fluoride and sodium fluoride; and

a second step of subjecting the resulting oxide film to an electrodeposition treatment selected from the group consisting of electroplating and electrolytic coloring or a combination thereof.

4. A process for surface treatment of an aluminum alloy, according to claim 3, wherein the amount of sodium hydrogenphosphate, tribasic sodium phosphate, sodium citrate, sodium tartrate, sorbitol, potassium fluoride and sodium fluoride is 0.2 to 0.5 mol, 0.2 to 0.4 mol, 0.1 to 0.75 mol, 0.1 to 0.55 mol, 0.25 to 0.75 mol, 0.1 to 0.75 mol and 0.1 to 0.75 mol, respectively.

5. A process for making a decorative wheel cover using an aluminum alloy containing Si, the process comprising the steps of:

buffing a surface of the aluminum alloy;

forming an anodized film on the buffed surface by subjecting the buffed surface to an anodizing treatment using an electrolyte comprising;

(i) at least one compound containing an anion capable of coordinating as a ligand on a metal ion to form a complex during said anodizing treatment selected from the group consisting of sodium hydrogenphosphate and tribasic sodium phosphate,

(ii) at least one salt of an organic acid containing an oxyacid anion selected from the group consisting of sodium citrate and sodium tartrate, or sorbitol, and

(iii) at least one halide selected from the group consisting of potassium fluoride and sodium fluoride;

subjecting the anodized film to Ni plating to form a nickel plating film; and

subjecting the surface of the Ni plating film to Cr plating.

6. A process according to claim 5, wherein the amount of sodium hydrogenphosphate, tribasic sodium phosphate, sodium citrate, sodium tartrate, sorbitol, potassium fluoride and sodium fluoride is 0.2 to 0.5 mol, 0.2 to 0.4 mol, 0.1 to 0.75 mol, 0.1 to 0.55 mol, 0.25 to 0.75 mol, 0.1 to 0.75 mol and 0.1 to 0.75 mol, respectively.

7. A spiral scroll member for a compressor that comprises a casing and a relatively rotating a pair of spiral scroll members, comprising:

a spiral scroll member made of an aluminum alloy containing Si; and

an anodized film formed on the surface of the spiral scroll member by subjecting the spiral scroll member to an anodizing treatment using an electrolyte comprising;

(i) at least one compound containing an anion capable of coordinating as a ligand on a metal ion to form a complex during said anodizing treatment selected from the group consisting of sodium hvdrogenphosphate and tribasic sodium phosphate,

(ii) at least one salt of an organic acid containing an oxyacid anion selected from the group consisting of sodium citrate and sodium tartrate, or sorbitol, and

(iii) at least one halide selected from the group consisting of potassium fluoride and sodium fluoride,

wherein the amount of sodium hydrogenphosphate, tribasic sodium phosphate, sodium citrate, sodium tartrate, sorbitol, potassium fluoride and sodium fluoride is 0.2 to 0.5 mol, 0.2 to 0.4 mol, 0.1 to 0.75 mol, 0.1 to 0.55 mol, 0.25 to 0.75 mol, 0.1 to 0.75 mol and 0.1 to 0.75 mol, respectively.

8. A cylinder block for an internal combustion engine, comprising:

a cylinder block wherein an inner circumferential surface of a cylinder is made of an aluminum alloy containing Si;

an anodized film formed on the inner circumferential surface of the cylinder by subjecting the cylinder to an anodizing treatment using an electrolyte comprising;

(i) at least one compound containing an anion capable of coordinating as a ligand on a metal ion to form a complex during said anodizing treatment selected from the group consisting of sodium hvdrogenphosphate and tribasic sodium phosphate,

(ii) at least one salt of an organic acid containing an oxyacid anion selected from the group consisting of sodium citrate and sodium tartrate, or sorbitol,

(iii) at least one halide selected from the group consisting of potassium fluoride and sodium fluoride,

wherein the amount of sodium hydrogenphosphate, tribasic sodium phosphate, sodium citrate, sodium tartrate, sorbitol, potassium fluoride and sodium fluoride is 0.2 to 0.5 mol, 0.2 to 0.4 mol, 0.1 to 0.75 mol, 0.1 to 0.55 mol, 0.25 to 0.75 mol, 0.1 to 0.75 mol and 0.1 to 0.75 mol, respectively; and

a Ni/SiC plating film provided on the anodized film.

9. A cylinder block for an internal combustion engine, according to claim 8, wherein the Si content of the anodized film is equal to or less than 8%.

10. An aluminum alloy decorative cover comprising an aluminum alloy containing Si and having a buffed surface;

an anodized film formed on said buffed surface of said aluminum alloy by subjecting the buffed surface to an anodizing treatment using an electrolyte comprising;

(i) at least one compound containing an anion capable of coordinating as a ligand on a metal ion to form a complex during said anodizing treatment selected from the group consisting of sodium hydrogenphosphate and tribasic sodium phosphate,

(ii) at least one salt of an organic acid containing an oxyacid anion selected from the group consisting of sodium citrate and sodium tartrate, or sorbitol, and

(iii) at least one halide selected from the group consisting of potassium fluoride and sodium fluoride,

wherein the amount of sodium hydrogenphosphate, tribasic sodium phosphate, sodium citrate, sodium tartrate, sorbitol, potassium fluoride and sodium fluoride is 0.2 to 0.5 mol, 0.2 to 0.4 mol, 0.1 to 0.75 mol, 0.1 to 0.55 mol, 0.25 to 0.75 mol, 0.1 to 0.75 mol and 0.1 to 0.75 mol, respectively;

a Ni plating film provided on said anodized film; and

a Cr plating film provided on said Ni plating film.

11. An aluminum alloy decorative cover according to claim 10, wherein the decorative cover is a crankcase cover for a motorbike.