Apparatus and method for anodising an inner surface of a tube

Abstract

An anodization apparatus is disclosed that includes an anode holder adapted to hold a tube, such that the tube is adapted to receive electrolyte and the tube has a first surface profile formed on an inner surface of the tube. The anodization apparatus also includes a cathode holder adapted to hold a cathode concentrically in the tube, such that the cathode has a second surface profile formed an outer surface of the cathode and the outer surface faces the inner surface of the tube. The cathode holder and the anode holder are adapted to supply electric potential of a predetermined current density to the cathode and the tube, respectively, and a surface area ratio between the first surface profile and the second surface profile is maintained within a predetermined range to facilitate formation of a homogenized anodized coat on the second surface profile.

1 . A method of anodising an inner surface of a tube, comprising:
 mounting the tube on an anode holder, wherein the tube has a first surface profile formed on an inner surface of the tube;   mounting a cathode on a cathode holder to place the cathode concentrically inside the tube, wherein the cathode has a second surface profile formed an outer surface of the cathode and the outer surface faces the inner surface of the tube;   pumping an electrolyte through an annulus between the outer surface and the inner surface; and   applying an electric potential across the tube and the cathode via the anode holder and the cathode holder, respectively,   wherein a surface area ratio between the first surface profile and the second surface profile is maintained within a predetermined range to facilitate formation of a homogenised anodized coat on the first surface profile.   
     
     
         2 . The method of  claim 1 , comprising:
 oscillating, by a linear drive unit of the cathode holder, the cathode linearly at a predetermined rate along a length of the tube.   
     
     
         3 . The method of  claim 1 , comprising:
 rotating, by a rotational drive unit of the cathode holder, the cathode at a predetermined rotational speed inside the tube.   
     
     
         4 . The method of  claim 1 , wherein moving the cathode comprises maintaining a predetermined distance between surface profiles of the cathode and the tube. 
     
     
         5 . The method of  claim 1 , wherein the predetermined range of surface area ratio is 9:1 to 1.5:1. 
     
     
         6 . A tube having a first surface profile formed on inner surface and an anodized coat formed on the first surface profile, by the method as claimed in  claim 1 . 
     
     
         7 . An anodization apparatus comprising:
 an anode holder adapted to hold a tube, wherein the tube is adapted to receive electrolyte and the tube has a first surface profile formed on an inner surface of the tube; and   a cathode holder adapted to hold a cathode concentrically in the tube, wherein the cathode has a second surface profile formed an outer surface of the cathode and the outer surface faces the inner surface of the tube,   wherein the cathode holder and the anode holder are adapted to supply electric potential of a predetermined current density to the cathode and the tube, respectively, and   wherein a surface area ratio between the first surface profile and the second surface profile is maintained within a predetermined range to facilitate formation of a homogenised anodized coat on the second surface profile.   
     
     
         8 . The anodization apparatus of  claim 7 , comprising a power source adapted to apply the electric potential of the predetermined current density across the cathode holder and the anode holder. 
     
     
         9 . The anodization apparatus of  claim 7 , comprising a pumping unit adapted to pump the electrolyte through the tube. 
     
     
         10 . The anodization apparatus of  claim 7 , wherein the cathode holder comprising:
 a pair of clamp contacts configured to supply the electric potential to the cathode;   a linear drive unit configured to oscillate the cathode linearly at a predetermined rate along a length of the tube; and   a rotational drive unit configured to rotate the cathode at a predetermined rotational speed inside the tube.   
     
     
         11 . The anodization apparatus of  claim 7 , wherein the anode holder comprising a pair of clamp contacts configured to supply the electric potential to the cathode. 
     
     
         12 . The anodization apparatus of  claim 7 , wherein a magnitude of the predetermined current density is in a range of 4 to 20 amps/square foot. 
     
     
         13 . The anodization apparatus of  claim 7 , wherein the first surface profile and the second surface are rifles. 
     
     
         14 . The anodization apparatus of  claim 7 , wherein
 the predetermined rate is in a range of < >,   the predetermined rotational speed is in a range of 1 to 50 Rotations Per Minutes (RPM).   
     
     
         15 . The anodization apparatus of  claim 7 , wherein
 the cathode is made of Aluminium alloy.   
     
     
         16 . The anodization apparatus of  claim 7 , wherein the predetermined range of the surface area ratio is 9:1 to 1.5:1.