US 9,809,894 B2
Metal treatment
Andrew Derek Turner, Abingdon (GB)
Assigned to Accentus Medical Limited, Didcot (GB)
Appl. No. 13/979,459
Filed by Andrew Derek Turner, Abingdon (GB)
PCT Filed Jan. 13, 2012, PCT No. PCT/GB2012/050068
§ 371(c)(1), (2), (4) Date Aug. 20, 2013,
PCT Pub. No. WO2012/095672, PCT Pub. Date Jul. 19, 2012.
Claims priority of application No. 1100605.3 (GB), filed on Jan. 14, 2011; and application No. 1106733.7 (GB), filed on Apr. 21, 2011.
Prior Publication US 2013/0319869 A1, Dec. 5, 2013
Int. Cl. C25D 11/16 (2006.01); C25D 21/12 (2006.01); C25D 11/02 (2006.01)
CPC C25D 11/02 (2013.01) [C25D 11/024 (2013.01); C25D 11/16 (2013.01); C25D 21/12 (2013.01)] 7 Claims
OG exemplary drawing
 
1. A method of anodising a metal object, the method comprising:
contacting the metal object with an anodising electrolyte, and pre-anodising the surface so as to grow a thin oxide film of consistent thickness on the surface by applying an anodising voltage and gradually increasing the anodising voltage up to a maximum pre-anodising voltage, and then holding at this voltage until the current has significantly decreased, wherein the maximum pre-anodising voltage relative to an Ag/AgCl electrode is less than 10V;
making electrical measurements on the thin oxide film during the pre-anodising step, and hence deducing the surface area of the metal object; and
then anodising the metal object using conditions calculated on the basis of the deduced surface area;
wherein the surface area is deduced from a measurement of electrical current during the pre-anodising step, wherein the variation in electrical current with time as the applied voltage is increased has at least one plateau portion wherein the current is substantially constant over a range of applied voltage during the pre-anodising step, and the measurement of electrical current is the average current over a plateau portion of the current variation.