How Does Weld-Thru Primer Work?

Posted: April 3, 2020 By: MattM

When restoring vehicle or closing up metal where there is an area that is going to be boxed in or hidden you need to consider the bare metal on the backside of the weld joint and how you can be sure it won’t rust over time. Normal primer isn’t rated to be able to withstand high temps and it will peel, flake and also won’t allow you to weld around them. So how the heck does weld-thru primer work and is it actually worth it?

A good weld-thru primer is generally used in an area metal is sandwiched or hidden when welding and you can’t get in to prime or paint it after welding. This is especially helpful on lap joints, boxed in areas, or tight corners. A good weld thru primer has a binder that is conductive and will allow you to strike an arc. Commonly most weld thru primers use a zinc or copper binder, but some higher end primers will use an organic binder that will actually leave a corrosion resistant film or coating after they burn off during the welding process. We prefer to use our Self-Etching Weld Thru primer for the ultimate corrosion protection in hidden areas on weld seams. The self-etching properties allow it to grab on and bite into the metal to avoid adhesion issues when heated and it also leaves a corrosion inhibiting coating after welding on the weld seam that will keep it from welding over time. This combination of two staple products in the coating world allows you to have a one-step process when preparing weld joints and seams. We like to clean all surfaces to bare metal and abrade before coating to give for the best adhesion.

In closing want to reinforce that whatever Weld-Thru primer you’re choosing make sure that it either has a metallic or organic binder that will help with conductivity when welding. Some lower end weld-thru primers nothing more than a standard primer relabeled and will burn, bubble, and peel when you weld near them! To see all of our surfaced prep products visit our site HERE.

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