Chemical cleaning of Aluminum 2219 -O.

[waqasmalik]

I have asked this question on linkedin but i received no responses so i am copying the same here.

Hi all, my workshop is involved in TIG welding of aluminum 2219-O weldment, having diameter 600 mm and length of 500 mm. Joint is prepared by machining which uses cutting lubricants so we clean the joint prior to welding by chemical phenomenon. First the weldment is dipped for one minute into a heated solution ( 70 degrees centigrade) of 10% NAOH and 90% water, being prepared in SS tank. Then weldment is washed by tap water,afterwards, weldment is dipped into concentrated nitric acid solution for one minute which is 50% nitric acid and 50 % water. After this material is ready for welding.

I have two questions .

1) Does the procedure/technique described above is valid?
2) If yes, then what will the life of these solutions? I mean, should i clean the material only once and then replace all the solution with new one?

Any response will be highly acknowledged.

 

[CoryPad]

1. 10 % NaOH in water is a reasonable solution to remove organic contamination from cutting lubricants. The 50 % nitric acid must be to remove oxides and activate the surface, so that the aluminium has lower resistance and will be more readily welded.

2. The life of the solutions will depend on the volume of solution and the immersion time of the sample. You should contact a chemical company like Henkel or Chemetall to help you establish periodic bath maintenance.