ISO 8080:2021 pdf download – Aerospace — Anodic treatment of titanium and titanium alloys — Sulfuric acid process.
4.2 Preparation for anodizing 4.2.1 Parts shall be thoroughly alkaline cleaned to ensure that all surfaces are free from contaminants such as grease, oil and mill markings. 4.2.2 Chlorinated solvents and methyl alcohol shall not be used for degreasing. 4.2.3 Parts shall be firmly attached to the racking device. Contact areas shall be kept as small as possible and, when practicable, shall be on a surface not required to be coated. When parts are to be coated on all surfaces, contacts shall be located on areas indicated on the drawing. 4.2.4 Parts shall be oriented so as to minimize gas entrapment during processing. 4.2.5 After cleaning, parts shall be etched for a minimum duration to guarantee surface activation in an acid pickling solution (see 4.1.7) and then rinsed thoroughly in cold running water. Heavily scaled parts which do not provide a clean, bright surface after the treatment outlined above may require fine alumina gritblasting or pretreatment in an oxidizing alkaline solution prior to etching. NOTE Surface activation is correct when the surface is visually clean and bright. 4.2.6 As an alternative, a mechanical activation can be used for surface preparation if agreed between the original equipment manufacturer (OEM) and the processor. 4.3 Anodizing procedure 4.3.1 The parts shall then be immersed in the anodizing solution. The parts shall be made the anode and the tank, or auxiliary plates, the cathode. Current shall be applied to reach the desired coloration. Recommended voltage cycle: from 15 V to 20 V for a period of 15 min or until the desired coloration has been achieved. The recommended initial current density should be approximately 0,2 A/dm 2 , with a reduction to an approximate value of 0,05 A/dm 2 over the greater part of the anodizing cycle.
4.3.2 During processing of intricate parts, the solution should be agitated in order to minimize entrapment of gas in pockets and blind holes. If necessary, parts should be repositioned periodically to bring the electrolyte into contact with uncoated areas and to prevent attack at the liquid/gas interface in pockets and blind holes. 4.3.3 After completion of the anodizing cycle, parts shall be rinsed thoroughly in cold, running water, then rinsed in clean, hot water and dried. 4.3.4 If subsequent surface treatments are to be applied, parts should be handled and stored in such a manner as to avoid them being contaminated.