Method of anodizing a part made of aluminum alloy

• US 20030196907A1
• Filed: 04/21/2003
• Published: 10/23/2003
• Est. Priority Date: 04/22/2002
• Status: Abandoned Application

• Current Assignee: Messier-Bugatti (Safran SA)
• Original Assignee: Messier-Bugatti (Safran SA)
• Inventors: Viola, Alain
• Application Number:
  US10/419,152
• Publication Number:
  US 20030196907A1
• Time in Patent Office: Days
• US Class Current: 205/324
• CPC Class Codes: C25D 11/08 containing inorganic acids
• CPC Class Codes: C25D 11/10 containing organic acids
• CPC Class Codes: C25D 11/12 Anodising more than once, e.g. in different baths

Abstract

The invention provides a method of anodizing a part made of aluminum alloy. According to the invention, the method comprises the following steps in succession:

providing an aqueous anodizing bath essentially comprising sulfuric acid at a concentration lying in the range 55 g/l to 85 g/l, and excluding the presence of any phosphoric acid or any boric acid;

maintaining said bath at a constant temperature essentially lying in the range 15° C. to 27° C.;

dipping said part into said bath;

applying a voltage to said part dipped in said bath, the voltage lying essentially in the range 5 V to 30 V, with low current density on said part; and

maintaining said part in said bath until a coating of desired thickness has been obtained, which thickness lies substantially in the range 1 μm to 3 μm.

Claims

1. / A method of anodizing an aluminum alloy part, the method comprising the following steps in succession:

providing an aqueous anodizing bath essentially comprising sulfuric acid at a concentration lying in the range 55 g/l to 85 g/l, and excluding the presence of any phosphoric acid or any boric acid;

maintaining said bath at a constant temperature essentially lying in the range 15°

C. to 27°

C.;

dipping said part into said bath;

applying a voltage to said part dipped in said bath, the voltage lying essentially in the range 5 V to 30 V, with low current density on said part; and

maintaining said part in said bath until a coating of desired thickness has been obtained, which thickness lies substantially in the range 1 μ

m to 3 μ

m.

2. / A method according to claim 1, in which the concentration of sulfuric acid in the bath lies essentially in the range 57 g/l to 67 g/l, and is preferably close to 62 g/l.

3. / A method according to claim 1, in which the bath is maintained at a constant temperature close to 22°

C.

4. / A method according to claim 1, in which the voltage applied to the part dipped in the bath is fixed on a constant value throughout the duration of the anodizing treatment, said constant value lying in the range 5 V to 30 V.

5. / A method according to claim 4, in which the constant value of the voltage lies in the range 7 V to 20 V.

6. / A method according to claim 1, in which the voltage applied to the part dipped in the bath is initially fixed to a first constant value, and then after a predetermined duration, to a second constant value that is higher than the first, said first and second constant values both lying in the range 5 V to 30 V.

7. / A method according to claim 6, in which the first constant voltage value lies in the range 5 V to 11 V, and the second constant voltage value lies in the range 15 V to 30 V.

8. / A method according to claim 1, in which the current density on the part dipped in the bath remains well below 100 A/m².

9. / A method according to claim 8, in which the current density is essentially less than 80 A/m², preferably lying in the range 30 A/m² to 70 A/m².

10. / A method according to claim 1, in which the aqueous anodizing bath also contains an acid alcohol having one to three acid functions, at a concentration lying in the range 12 g/l to 22 g/l.

11. / A method according to claim 10, in which the acid alcohol used in the that is tartaric acid or citric acid, and the concentration of said acid alcohol lies essentially in the range 12 g/l to 17 g/l.

12. / A method according to claim 1, in which the part to be treated is subjected to preliminary degreasing/pickling treatment prior to being dipped in the bath.

13. / A method according to claim 1, in which the treated part is subjected to subsequent treatment of sealing the coating.