Weld-Through Primer Guidelines: Mitsubishi - UPDATE

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 Mitsubishi recommends and where this information can be found.

Mitsubishi recommends the use of weld-through primer for squeeze-type resistance spot welding (STRSW) but does not specify the use of it when GMA welding. This information is typically located in the service manual under: Service information ➤ 9-Base Of Body Repair ➤ Corrosion Protection ➤ Anti-Corrosion Treatment At The Time Of Body Repair Work.

This document details the application of weld-through primer (spot sealer) to spot welded points and states:

  • "In order to prevent corrosion from occurring at the contact surfaces of panels which are spot welded, apply an electroconductive spot sealer.
  • Remove all paint, etc., from the areas to be spot welded by using sandpaper or a pneumatic belt sander.
  • Use a brush to apply spot sealer to the contact surfaces of the panels (both the new panel and the panel remaining on the body) to be spot welded.
  • The spot welding can be done as the spot sealer is dry to the touch. Dry to the touch: 30 minutes or less at 20°C (68°F)."

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 Mitsubishi information, check out the Mitsubishi OEM information page.

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