What is a key characteristic of Weld-Thru primers?

A key characteristic of Weld-Thru primers is that they restore zinc protection that may be lost or burned away during the welding process. When welding, the intense heat can strip away protective coatings, exposing bare metal to the environment, which increases the risk of corrosion. Weld-Thru primers are formulated specifically to provide a layer of corrosion resistance by incorporating zinc, which acts as a sacrificial anode, sacrificing itself to protect the underlying steel. This characteristic is essential as it maintains the integrity of the metal and prolongs the lifespan of the repair work.

Other options do not accurately describe the primary function of Weld-Thru primers. While they may indeed be left intact after application, they are not solely intended for enhancing paint finish. Their primary purpose extends beyond merely acting as a surface for the final paint coat. Additionally, these primers are specifically designed for use on bare metal surfaces impacted by welding and are not suitable for direct application on painted surfaces. Thus, the right answer highlights the unique protective property that is critical for automotive body repair.