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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 Rolls-Royce recommends and where this information can be found.
Rolls-Royce recommends the use of weld-through primer on steel when performing GMA plug welds (Rolls-Royce calls this MAG and spot welding). This information can be found in the vehicle-specific body repair manual ➤ Repair Instruction ➤ Unified Parts Group ➤ 41 Body ➤ 41/00 Body ➤ Contents of Body, General ➤ Welding and soldering steel components. Some steps for welding preparation per Rolls-Royce:
- "Remove the paint in an area of approximately 30 mm around the weld seam or spot.
- The zinc layer underneath must be removed during the MAG welding method.
- Remove the paint on the reverse side of the weld seam or spot.
- Coat all metal overlaps and welding spot flanges with weld-through primer."
Rolls-Royce recommends Inox spray welding primer. This can be found in the same 41/00 Body area in a document called Overview of Consumables.
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.
Additional I-CAR Collision Repair News you may find helpful:
- Step-By-Step: Accessing Rolls-Royce Repair Information
- Weld-Through Primer Guidelines
- Welding And MIG Brazing Hotspot