James Meyer, a Toyota Collision Repair & Refinishing Training team member, was the lead author of this article.
Snow, hail, rain, wind, and sub-freezing temperatures—winter can be a harsh environment to our customers’ vehicles! In many parts of the country, winter is the time when weather elements are at their toughest. You may have heard of the term “winter brine”— this is a mixture of magnesium and calcium chloride used on the roads in colder climates for de-icing purposes and for safer travel conditions. Winter brine can be highly corrosive to vehicle components. This is because of the high amount of acid molecules that result from mixing those chemicals with water and oxygen.
Unfortunately, vehicle components that can be most susceptible to rust and corrosion are parts that have been subjected to collision repair welding. That is why using quality products and practicing good corrosion prevention techniques during a collision repair is so important, and why I advise all technicians—no matter what time of year or where in the country they live—to be diligent about building corrosion prevention into each repair and component replacement. This helps ensure that they will deliver a safe, high-quality repair that will last.
On Toyota, Lexus and Scion vehicles, I recommend following the original manufacturer application specifications for chip-resistant paint coatings, seam sealer and cavity wax, which can be found in model-specific Collision Repair Manuals. Apply two-component (2K) epoxy or direct-to-metal (DTM) primer to bare metal to replicate factory e-coat where necessary, and weld-through primers at flange welding locations. These materials, when used and applied properly, help protect against the elements and ensure the longevity of your repairs.
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Since the use of zinc-rich weld thru primer has a bit of mystery behind it, let’s get into some details of when and how to build corrosion prevention into a job with weld-thru primer. In Toyota training, we recommend using only a zinc-rich weld-through primer for your welding tasks. Keep in mind that zinc-based primers are more suitable than copper-based primers because of the zinc compatibility to the original Excelite steel coatings. This is because steel body components are manufactured using a zinc galvanizing process, and zinc primer bonds to this metal, referred to by its trade name ‘Excelite,’ better. Zinc is also more resistant to corrosion than copper.
At Toyota training we have some pretty simple and effective recommendations for properly using weld-through primer. The following are good procedural tips I recommend when applying weld-through primer.
· The metal must be clean; this helps the primer bond to the surface.
· Coat weld locations that are going to be joined together but won’t be accessible after welding.
· Follow product instructions for application technique and dry times.
· Allow the weld-through primer to dry completely before you begin the welding process. This gives the zinc the opportunity to properly bond to the metal.
· Remove any weld-thru primer that will affect adhesion of subsequent coatings and seam sealer. Most weld-through primers aren’t solvent resistant and can be washed away with cleaning solvent.
· Apply weld-through primer neatly and only to the areas that require the primer. Unsightly over-spray and unnecessary application should be avoided.
· Applying weld-thru primer to butt-weld flange edges is fundamentally unnecessary because it can inhibit weld flow and it serves no purpose at those locations.
After you have finished welding, clean the heat-affected zones (HAZ) around welds to remove burned or loose material, dress the welds appropriately then coat with epoxy primer. The reverse side of the HAZ should also be free of loose and burned coatings and coated with 2K epoxy primer or DTM and cavity wax.
Corrosion prevention techniques can be applied to a variety of different repair scenarios beyond welding. For example; outer body and structural components of Toyota, Lexus and Scion vehicles are coated with electro-deposition primer—also referred to as e-coat. E-coat is an excellent corrosion protection material and should be left intact whenever possible. If you have to remove e-coat during a repair remember, you can replicate it with 2K epoxy or DTM primer.
If you are curious about how your corrosion prevention techniques are holding up, you can put your present corrosion prevention techniques and materials to the test by preparing sample panels and subjecting them to simulated weathering conditions to see how they hold up.
If you are interested in learning more about Toyota, Lexus and Scion collision repair and refinish specifications and recommendations, we offer hands-on instructor-led training taught by our expert staff of trainers. Online courses are also available. Find out more about our Collision Repair & Refinish Training and read additional helpful information, beyond the scope of this article, directly from Toyota on the internet atcrrtraining.com.
