Weld-Through Primer Guidelines: BMW/Mini

Weld-through primers are generally a zinc-based product that are applied to the mating surfaces prior to welding. Corroding zinc forms zinc oxide which protects the steel. This is called sacrificial corrosion. For a quality weld to be made it’s required that the weld-through primer be removed from the direct weld zone before welding the joint when GMA welding. Many OEMs have a position on when and how to use weld-through primer or when it shouldn’t be utilized. Let’s see what BMW/Mini recommends and where this information can be found.

BMW/Mini recommends the use of weld-through primer on steel when performing MAG and spot welding. This information can be found in the vehicle-specific body repair manual in the Welding Steel Components document. Some steps for weld preparation are as follows:

  • Remove the paint approximately 30 mm around the area to be welded.
  • If performing MAG welds remove the zinc layer also.
  • Remove the paint on the backside of the weld.
  • Coat all metal overlaps with weld-through primer.
  • Perform a shear test on sample metal to determine the optimum electrode contact force.

Use the vehicle-specific body repair manuals to determine which type of welding is required for the repair you are performing. Failure to follow OEM procedures will sacrifice the safety and quality of the repair.

For additional BMW/Mini information, check out the following pages:
BMW OEM Information
Mini OEM Information

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