Metal finishing Q&As since 1989

-----

Different results anodising aluminum grades 6061 vs 6082 using 'home setup'

2006

I would appreciate some advice on anodizing ('home setup').
I am getting the following results doing clear anodizing: on 6061-T6 alloy, the anodize is quite nice looking (I estimate it to be around 1 mil thick by the way the parts fit). On 6082-T6, it comes out very disappointing - powdery looking, almost ash-white. Can you explain the difference or is this to be expected? My setup is as follows (please don't laugh - just an experiment before I go and spend lots on a pro setup): I'm using a 24Amp-hour battery [yes , you read correctly, not a charger (is this OK?)] . I have a sulfuric acid bath containing about 6 liters of solution (one part acid and 5 parts distilled water). My cathode comprises a two 2" x 1/16" strips of 6061-T6 aluminum plates running underneath the anode. The anode is connected via a .25" tube to the bus bar. The parts gas nicely for about 15 minutes and then I take the parts out and 'boil' them on the stove in hot water. The temperature of the tank starts off at about75 °F, but gets to about 90degrees by the time I'm finished. BTW, is the pungent smelling fumes bad for you? (I am working in the open air). Besides wearing gloves, safety glasses (you can't replace your eyes) , is there any advice on handling of chemicals. I have read as much as I can on the subject without any books, so I wanted to try this very rudimentary approach first. I do have the Mil specs printed out and some safety sheets on the acids. Oh, I am not etching the parts which are very clean from having been tumbled first and then thoroughly washed.
I am mostly concerned with the difference in the finish of the 2 alloys, and is the battery absolutely totally unsuitable for a trial? The parts are less than 0.5ft sq. Interestingly, without etching, the 6082T6 part actually got smaller by about 0.0004" per side but not on 6061?
Thanks a 'mil' for any advice.

Michael Georgiadis
Hobbyist - KZN, South Africa