Author : Kareem Ahmed, Jaleel
Preparing Aluminum Alloys to Spot Welding by using immersion coating (Electrical Resistance Welding).
journal of kerbala university,
2007, Volume 3, Issue 2, Pages 164-172
It is the first time that immersion coating phenomenon used for preparing aluminum alloys surface for spot welding. Concentrated aqueous alkaline sodium zincate solution was used to deposit zinc at room temperature and replace an equivalent weight of aluminum from the alloy (G3/5052 or A5/3003) surface which is underneath the electrical insulator aluminum oxide layer which acts as inhibitor for spot welding results in destroying its link to the surface and fall down in the solution as visual white powder, it is similar to shaving process.Zinc coat is then removed by 50% nitric acid. The electrical resistance of the new conducting surface results from this treatment shows a linear relation ship against time up to 30 hours from the time of removal zinc coat according to the equation.
Y= 0.6 X + 3.5
and this indicates that the growth of aluminum oxide is regular during the first 30 hours from the time of exposure aluminum alloy surface to atmosphere. After this period (30 hours) the oxide film start to completion and its electrical resistance tends to be constant. The tensile strength of the welding spot shows a maximum value after 3 hours (19.3 kg/mm2) from the time of zinc coat removal (from the time of exposure of aluminum alloy to the atmosphere), but a linear relationship is found between tensile strength vs. time obeys the following equation:-Y= - 0.053X + 16.23 Where X between 6-48 hours after zinc coat removal.