by Bob Beranek
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I read with interest this week about the new 2015 Ford F-150 truck having a “mostly” aluminum body. That word “mostly” is what really piqued my interest. Jaguar is another vehicle that has a “mostly” aluminum body, although the pinchweld is not, so the bonding and the type of urethane doesn’t cause major concerns. The Audi A8 and TT coupe have all aluminum bodies and special adhesives and prepping are called for to prevent galvanic corrosion.

To learn more about the F-150, I emailed my friend and colleague from Carlex—Rod Watson. He informed me that indeed the truck’s pinchweld is aluminum and that the manufacturer uses Dow urethane. With that knowledge it is apparent that aluminum/galvanic corrosion will be a concern when replacing the windshield on these vehicles.

The reason I was so concerned about this revelation is that, unlike the Jag and the Audi, the F-150 is the best-selling vehicle on the road, and we will be working on them frequently. We will need to have specific and clear instructions from all of our adhesive suppliers on how to deal with the prepping of the aluminum body.

Obviously, Ford has done their research and knows how to bond the glass to the body without causing corrosion. The company’s paint procedures are such that no matter what product used, the coating will protect the aluminum from oxidation. Our concern must be what happens when we get the vehicle for glass replacement? What precautions must we take to protect the vehicle from premature corrosion? What products must we use to avoid dissimilar metal interaction?

To answer these questions, I went to the experts, the adhesive manufacturers.

Dale Malcolm from Dow says that the key to reduce galvanic corrosion is to “clean and seal the scratch as soon as possible, especially with aluminum.” His product Betaseal™ 5504G All-In-One Primer is the company’s answer to sealing the scratch. Dale’s suggestion for the best results is to seal the scratch immediately. The longer the scratch is exposed to oxygen the more prepping the tech must do. For example, if the scratch is allowed to stay exposed for a long period of time, follow these steps:

—Clean with an abrasive pad or abrasive pen* to bright shiny metal;

—Wipe with 100 percent pure acetone; and

—Apply two coats of 5504G allowing two to ten minutes between coats, depending on ambient temperature.

Bob Stenzel of Sika says that their products and procedures have not changed much for several years:

—Abrade the scratch with plastic abrasive pad (ScotchBrite);

—Wipe the scratch with Aktivator Pro® and let dry three to ten minutes, depending on ambient temperature; and

—Apply a coat of Sika® Primer-206 G+P and allow to dry 10 minutes.

SRP adhesives work similar to the others:

—Small scratches (less than 1 inch by 1 inch) require the removal of any existing corrosion;

—Wipe with 100 percent acetone and allow to dry;

—Apply the SRP 5025 Primer; and

—Allow it to “flash off” and dry thoroughly for ten minutes depending on ambient temperatures.

As Dale says, the key is to clean and seal it immediately. Clean it with acetone or recommended product and seal it with the metal primer. The use of the procedures above should make the introduction of aluminum vehicles rather uneventful. My thanks to Dale Malcolm and Bob Stenzel for their expertise.

*The abrasive pen Dale discovered was a product marketed by ProMotorCarProducts.com. It is a glass filament abrasive that can reach into small areas for removal of corrosion or contaminants. Though I haven’t had a chance to use one yet, Dale says it is a really effective tool for use in our industry. If you have any experience with this product please e-mail me at bob@autoglassconsultants.com. I am very interested in hearing your feedback.