Aluminum Pretreatment to Improve Resistance Spot Weld Tiplife

The surface contact resistance of aluminum can be stabilized in a suitable micro-ohm range and this will prolong tiplife during spot welding. Alloys 2036-T4 and 5182-O were processed to give 75 micro-ohm surface resistance that would remain stabilized for storage times of at least ten weeks. The metal pretreatment consisted of conventional cleaning followed by a process to reoxidize to the desired micro-ohm level. The final step was a stabilization process consisting of a brief dip in mildly alkaline stearate solution, which produced a reacted monolayer of stearate above the existing oxide. The stearate monolayer stabilizes the contact resistance, presumably by preventing further oxide film-forming reactions.