Hi,

 I anodize aluminum and we use square Pt grid. However Pt strips or graphite plates are also applicable in this case. If I were You I would try Pt grid. I strongly recommend You to anodize samples smaller than Your cathode.

Wojciech is correct. Pt mesh is the best choice and ideally the area of the cathode should be larger than the area of the anode. if you have a chatode smaller than the anode you may have some inhomogeneities in the anodic film you are growing, especially on the edges of the sample due to variations in the electric field across the sample

Domenico is right. Size of the cathode is crucial for anodic oxides growth, sometimes too smal cathode can cause samples "burning" - anodic dissolution of anode instead of oxide film growth.

If You have any practical or theoretical questions don't hestitate to write message to me and I will be happy to anwser. I wish You luck with Your research!

I anodized Ti recently for me I strongly recommend You to anodize samples smaller than Your cathode.i sused a lead cathode good lacke

I would be careful with lead. If You will use electrolyte with fluorides or HF Pb-F complexes may be formed. These will be for sure negatively charged and attracted by the anode. Furthermore, these anions will be incorporated into grown oxide and may affect the regularity of nanopores / nanotubes as well as their morphology. So Pt is better cathode, of course while it's larger than the anode.

it is preferable that the cathode is a circular current to reach the shower the entire surface of the anode

Your feedback is much appreciated. Thank you.

Hi,

I anodized aluminum and we use Stainless Steel - 316 for Cathode& anode.

Area of cathode should be larger than anode. It is better to use platinium plates for anodisation of single surface.

Hi,

I make titanium dioxide nanotubes using Pt plate or a long platinum wire twisted in a spiral form for cathode. Like everybody told, area should be larger than the anode area. I arrange the two electrodes always parallel, with anode pressed against an O-ring in an electrochemical cell, leaving an area exposed to the electrolyte, if I want to have a certain surface of titanium coated with nanotubes.

I am currently working in Al anodization and I have to say thanks for your tips. I observed that when I use an Al anode with the same size that cathode, the anodization is not uniform. Today I made it short and both electropolishment and anodization was almost perfect. I have some problems with removing remaining Al when using a saturated HgCl2 solution. The PAA becomes gray...I gues that formed amalgam is going to nanopores... Still working in optimization. Best regards. 

Hello,

we have successfully synthesized a well aligned nanotubes on Ti6Al4V alloys ( surface area : 0.94 cm²) with a graphite as counter electrode ( diameter : 7mm) in ethylene glycol , NH4F and H2O electrolyte at 60 V for 0.5 to 2h..

best regards

@Yasir F Joya,

            The counter electrode (CE) material used in the anodization process influences the formation of TiO2 nanotubes (TNT); different CEs produce different aspect ratio nanotubes. Different kinds of CEs such as iron, carbon, stainless steel, and aluminum are available. The TNT produced using stainless-steel cathode is short and have thin (5–10 nm), non-uniform walls thickness, and their diameter seems to vary non-uniformly at the top and bottom, which results in conical shaped TNT. The aspect ratio obtained using an aluminum cathode is identical to that obtained using a carbon cathode. However, the top surface of the TNT obtained using the aluminum cathode is similar to that obtained using a stainless-steel cathode. The walls at the base of these TNTs seem to be stable but the top tends to collapse. The TNT formed using an aluminum cathode is much less stable than those obtained using a carbon cathode. When an iron cathode is used, well-organized TNT is formed with high aspect ratios. However, they are less stable than those produced using a carbon cathode. Using a carbon cathode produces nanotubes with higher aspect ratios, larger tube diameters, and longer tubes than nanotubes produced using other cathode materials. Furthermore, a carbon cathode produces nanotubes that are just as good as those produced using a platinum cathode and that have similar aspect ratios. However, carbon is considerably cheaper than platinum. Some researchers used wide variety of CEs including Ni, Pd, Pt, Fe, Co, Cu, Ta, W, C, and Sn for the development of TNT. Their results indicated that the nature of the cathode material plays a vital role in the appearance of surface precipitate.

            In addition, the over potential of the cathode is a critical factor, which affects the dissolution kinetics of the Ti anode, in turn controlling the activity of the electrolyte and morphology of the formed TNT. More the dissolved Ti in the electrolyte, the higher the electrolyte conductivity, which in turn helps to prevent debris formation. It appears that the different cathode materials led to the fabrication of different morphologies due to differences in their overvoltage within the test electrolyte. Hence, the arrangement of the cathode materials according to their stability in aqueous electrolytes is in the following order: Pt=Pd>C>Ta>Al>Sn>Cu>Co>Fe>Ni>W

            Apart from the nature of electrodes, the distance between working electrode (WE) and CE also influences the morphology of TNT. Enlargement of pore diameters, wall thickness, and inter-tubular spacing could be achieved by simply reducing the inter-electrode spacing under a fixed condition. The electrolyte conductivity and titanium concentration were found to strongly depend upon the electrode spacing, with the closer electrode spacing reflecting high conductivity and high titanium concentration. Electrolyte conductivity and titanium concentration are found to drastically increase with decreasing anode–cathode separation. Resulting TNT also tends to increase significantly, particularly observed in inter-tubular spacing as reducing the electrode spacing from 4.5 to 0.5 cm under a fixed electrolyte condition. Due to the combination effect of electrolyte properties and high field strength between the electrodes, the self-enlargement potential is believed to be a driving force for nanotube separation.

 Herewith attached some papers; hope which may help you to find the areas of both CE and working Ti electrode.

Article Effect of anodization parameters on the structural morpholog...

Article A Review on TiO2 Nanotubes: Influence of Anodization Paramet...

 The size must be greater than the anode, the shape is not important. Square / circular THE NATURE POSSIBLE Pt or graphite