Weld-Through Primer Guidelines: Mercedes-Benz

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 Mercedes-Benz recommends and where this information can be found.

This information can be found in the vehicle-specific body repair manual (BRM). Mercedes-Benz calls out the use of weld-through primer within sectioning and replacement procedures.

Per a 2023 Mercedes-Benz E450 B-Pillar procedure: "Coat insides of spot weld flanges with zinc dust paint."

Per a 2024 Mercedes-Benz C-300 quarter panel procedure: "Do not coat bonding surfaces with zinc dust paint."

Also, note that weld-through primer should not be used on aluminum. Mercedes-Benz refers to weld-through primer as zinc dust paint and recommends the use of their own brand.

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

For additional Mercedes-Benz information, check out the Mercedes-Benz OEM Information page.

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