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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 FCA/Stellantis recommends and where this information can be found.
FCA/Stellantis has a collision bulletin Approved Use Of Weld Through Primers. This document applies to all 2011 and newer models.
Per the Approved Use Of Weld Through Primers document:
- "Can only be used on ferrous metal components."
- "Weld through primer must be zinc based."
The document specifies that with squeeze-type resistance spot welding (STRSW):
- "FCA recommends the use of weld-through primer for all mating surfaces when using (STRSW) squeeze type resistance spot welding."
- "Weld-through primer is not to be used on mating surfaces where the combination of STRSW and adhesives (Weld Bonding) are being performed."
The document also specifies that with MIG/MAG welding (GMAW):
- "FCA recommends the use of weld-through primer on all internal flange surfaces / mating surfaces when using GMA Welding processes."
- "FCA requires the removal of all zinc weld-through primer completely from the weld zone before the welding process to reduce the possibility of porosity in the weld."
FCA/Stellantis recommends 3M 05917 Weld Thru II stated in: 31 - Collision Information ➤ Approved Materials ➤ Adhesives, Sealers And Additional Materials.
Please note, some new models do not have the Approved Use Of Weld Through Primers collision bulletin in the BRM. The recommendation for weld-through primer is found in the Welding And Weld Bonding and Corrosion Protection documents. These documents are found under: 31 - Collision Information ➤ Standard Procedures.
Always 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 sacrifices the safety and quality of the repair.
For additional FCA/Stellantis information, check out the following pages:
Alfa Romeo OEM Information
Chrysler OEM Information
Dodge OEM Information
Fiat OEM Information
Jeep OEM Information
RAM OEM Information
Additional I-CAR Collision Repair News you may find helpful:
- Step-By-Step: Accessing FCA/Stellantis Repair Information
- Weld-Through Primer Guidelines
- Welding And MIG Brazing Hotspot
Related I-CAR Courses
Original article published July 25, 2016