Aluminium alloy sheet with roughened surface
View Patent ↗There is disclosed a process for producing an aluminium alloy sheet, which comprises subjecting a surface of the sheet to anodising conditions to form on the surface an aluminium oxide barrier layer of thickness 10 to 50 nm and treating the oxide layer with an aqueous solution of alkali to remove the layer, thereby leaving a roughened surface on the alloy sheet.
1. A process for producing aluminium alloy sheet having a roughened surface which process comprises the steps of (1) subjecting a surface of the aluminium alloy sheet to be treated to anodising conditions to form on the said surface an aluminium oxide barrier layer having a barrier layer thickness in the range of from 10 to 50 nm, and (2) treating the aluminium oxide layer with an aqueous solution of alkali at temperature of 35° C. to 80° C. for a period of time sufficient to remove entirely said layer from the alloy surface thereby leaving a roughened surface on the alloy sheet.
2. A process according to claim 1 , wherein the aluminium alloy sheet is a sheet of alloy selected from AA1XXX and AA3XXX.
3. A process according to claim 2 , wherein the aluminium alloy sheet comprises a sheet of AA1050A, AA1200A or AA3103 alloy.
4. A process according to claim 1 , wherein in step (1) the aluminium alloy sheet is anodised using 20% phosphoric acid containing from 3 to 15 gl −1 aluminium at a temperature in the range of from 55° C. to 80° C. using a current density in the range of from 2 to 3 kAm −2 .
5. A process according to claim 1 , wherein a.c. anodising is used.
6. A process according to claim 1 , wherein d.c. anodising is used.
7. A process according to claim 1 , wherein the layer thickness of the aluminium oxide barrier layer produced on the surface of the aluminium alloy sheet is in the range of from 10 to 50 nm.
8. A process according to claim 7 , wherein the layer thickness of the aluminium oxide barrier layer produced on the surface of the aluminium alloy sheet is in the range of from 20 to 30 nm.
9. A process according to claim 1 , wherein the aluminium oxide barrier layer is non-porous.
10. A process according to claim 1 , wherein in step (2) the aqueous solution of alkali is selected from aqueous NaOH and aqueous KOH.
11. A process according to claim 10 , wherein the aqueous solution of alkali has a concentration in the range of from 1 to 10%.
12. A process according to claim 11 , wherein the aqueous solution of alkali is 2 to 5% NaOH.
13. A process according to claim 1 , wherein in step (2) the treatment is carried out for a period within the range of from 3 to 20 seconds.
14. A process according to claim 1 , wherein the aluminium alloy sheet is a sheet of AA1050A alloy and the surface of the alloy is treated to anodising conditions to form, on the said surface, a non-porous aluminium oxide layer having a layer thickness in the range of from 10 to 30 nm and wherein the aluminium oxide layer is treated, in step (2), with 3% aqueous NaOH at 60° C. for from 3 to 8 seconds.
15. A method of making a grained aluminium alloy sheet which comprises (1) subjecting a surface of a sheet of an aluminium alloy, to anodising conditions to form on the said surface an aluminium oxide barrier layer having a barrier layer thickness of from 10 to 50 nm; (2) treating the aluminium oxide layer with an aqueous solution of alkali at a temperature of 35° C. to 80° C. for a period of time sufficient to remove entirely said layer from the alloy surface thereby leaving a roughened surface on the alloy sheet, and (3) subjecting the roughened surface of the alloy sheet to graining.
16. A method according to claim 15 , wherein the aluminium alloy is an alloy selected from AA1XXX and AA3XXX alloys.
17. A method according to claim 15 , wherein the aluminium alloy is selected from AA1050A, AA1200A and AA3103 alloys.
18. A method according to claim 15 , wherein in step (1) the aluminium alloy sheet is anodised using 20% phosphoric acid containing from 3 to 15 gl −1 aluminium at a temperature in the range of from 55° to 80° C. using a current density in the range of from 2 to 3 kAm −2 .
19. A method according to claim 15 , wherein a.c. anodising is used.
20. A method according to claim 15 , wherein d.c. anodising is used.
21. A method according to claim 15 , wherein the layer thickness of the aluminium oxide barrier layer produced on the surface of the aluminium alloy sheet is in the range of from 10 to 50 nm.
22. A method according to claim 21 , wherein the layer thickness of the aluminium oxide barrier layer is from 20 to 30 nm.
23. A method according to claim 15 , wherein the aluminium oxide barrier layer is non-porous.
24. A method according to claim 15 , wherein in step (2) the aqueous solution of alkali is selected from aqueous NaOH and aqueous KOH.
25. A method according to claim 24 , wherein the aqueous solution of alkali has a concentration in the range of from 1 to 10%.
26. A method according to claim 25 , wherein the aqueous solution of alkali is 2 to 5% NaOH.
27. A method according to claim 15 , wherein in step (2) the treatment is carried out for a period in the range of from 3 to 20 seconds.
28. A method according to claim 15 , wherein in step (3) graining is electrograining in nitric acid.
29. A method according to claim 15 , wherein in step (3) graining is additive graining.
30. A method according to claim 29 , wherein the additive graining comprises applying to the roughened surface of the aluminium alloy sheet obtained in step (2) a coating selected from sol gel coatings or films that comprise a hydrophilic and hydrophobic layer.
31. A process for producing aluminium alloy sheet having a roughened surface which process comprises the steps of (1) providing an aluminium alloy sheet the surface of which has been subjected to anodising conditions to form on the said surface an aluminium oxide barrier layer having a barrier layer thickness in the range of from 10 to 50 nm, and (2) treating the aluminium oxide layer with an aqueous solution of alkali at temperature of 35° C. to 80° C. for a period of time sufficient to remove entirely said layer from the alloy surface thereby leaving a roughened surface on the alloy sheet.