We have a job on the horizon that requires spotwelding over alodined aluminum, 7075-T652 to 6061-T6. We have done some preliminary tests and have achieved satisfactory pull tests. However small surface cracks have been an issue. These we intend to work on with adjustments to the forge pressure and/or current decay perhaps. Normally we would chemically etch our parts but our customer wants the interface alodined beforehand in order to preclude inadequate coverage and bleedout. My question is are we on the right track or out in left field?

-- robert Watson (robert.watson@lmco.com), September 20, 2001

Answers

Since our specialty is aluminum welding, I think that you are on the right track. Increasing the cool rate should help. I would like to know the thickness of the two pieces. Good luck.

-- tom mitchell (info@atekweld.com), September 21, 2001.

Thanks for the prompt reply, the 7075 is .093" thick and the 6061 is .063". The cracks were small in nature and went unnoticed until later touched up with alodine which acted as a dye penetrant. Bob

-- Robert Watson (robert.watson@lmco.com), September 24, 2001.

Bob . I would like to know two more things. What class copper are you using and what configuration face on the electrode. we use class one copper and either a radius face or a dome electrode. The class one copper holds down surface heat and oxide pick up. The dome electrode gives you the 1/8 in. face for high current density start of the weld followed by increasing current density as the face settles into the surface. Let me know how you are progressing. Tom

-- tom mitchell (info@atekweld.com), September 24, 2001.