VIEWPOINT | A CLEANER, MORE FLEXIBLE METHOD TO PRETREAT ALUMINUM

Carmakers routinely use the zinc phosphate bath that cleans and prepares sheet steel for the paint process to achieve the same results for a vehicle's aluminum components. But sludge and surface quality issues quickly develop when the content of aluminum being pretreated surpasses 25%.

Two options are costly: retooling existing paint shop pretreatment operations or building new facilities. Henkel Corp. says its new BONDERITE Flex process is more cost-effective and environmentally sustainable. This process deposits a traditional zinc phosphate coating on steel and galvanized surfaces and in a second step a zirconium oxide coating on aluminum.

Henkel's BONDERITE Flex Process offers carmakers an inexpensive and environmentally sustainable alternative, according to Manish Dave, Henkel's director of surface treatment for North America. Already being used in Europe, the process reduces sludge dramatically and gives manufacturers the flexibility of handling up to 85% aluminum in the current pretreatment system. The new pretreatment process is now being introduced into the American market.

Dave says the BONDERITE Flex Process gives carmakers more flexibility in light-weighting vehicles by eliminating filtration issues and the high cost of retooling their pretreatment operations.

Why is the BONDERITE process taking hold in North America?

Future U.S. fuel economy standards are pushing carmakers to look at virtually every option to make their vehicles more fuel efficient. One of the most promising is light-weighting next-generation models through better design and the use of materials such as aluminum. Aluminum is about one-third the density of steel.

The Henkel process has been proven in Europe in recent years by high-end vehicle manufacturers. It's now being introduced to the mass-market producers in North America. Last year the BONDERITE Flex Process was launched at Chrysler (2013 model Chrysler 300, Dodge Challenger and Dodge Charger cars) and Ford (2013 model F-150 pickup trucks).

We believe the positive attributes of our zirconium oxide process on aluminum will make it a compelling choice as carmakers increase their use of lightweight components. We are promoting its value through our new Lighten Up campaign.

What are the limitations of the traditional zinc phosphate process?

Ducker Worldwide LLC predicts the average per-vehicle use of aluminum will jump 60% to 550 pounds by 2025.

As its proportion increases, so does the amount of sludge generated due to the etching of the aluminum surface during the deposition of the conversion coating. These sludge particles remain in suspension in the pretreatment bath. Unless they are filtered out, they can create rough surfaces, paint adhesion issues and the need for surface sanding and rework later on in the process. Any unfiltered particles could reduce the gloss level achievable after electrocoat.

When the total surface area of aluminum in the treatment bath approaches 25%, the amount of aluminum sludge created begins to overpower a traditional zinc phosphate system's filtration system. Controlling the additional sludge requires changes to the filtration system, higher free fluoride levels and greater bath agitation.

How is the BONDERITE process different?

We replace the traditional zinc phosphate coating on aluminum with a zirconium-based coating. This can be accomplished with little to no fundamental changes in the existing pretreatment equipment.

Because it is a two step treatment, the BONDERITE Flex Process reduces surface etching of aluminum in the traditional step and permits manufacturers to retain standard filtration systems and bath agitation rates even when the proportion of aluminum being treated climbs to 85%. The conversion coating on aluminum is then deposited in a second pretreatment stage. This means huge flexibility in the system's ability to handle a wide range of multi-material combinations without retooling existing paint shops or building new ones.

Because of its coating differentiation between substrates, the BONDERITE Flex Process provides corrosion protection for aluminum that is equal to or greater than what can be achieved using zinc phosphate, while maintaining performance on the other substrates.

What about costs?

When looking at a pound-to-pound comparison between a zirconium oxide coating and a zinc phosphate coating, zirconium oxide is higher. But the true costs lie in the complete process. The BONDERITE Flex Press uses less material, cuts waste, significantly eases the environmental challenges of sludge disposal and sharply reduces the need for manual rework on Class A surfaces. All contribute to reducing the overall operating cost of the process.

Our BONDERITE Flex process can be easily integrated into existing production lines without costly modifications. Production flexibility improves and overall costs go down. We believe there is literally no downside.

Learn more about how Henkel technologies can reduce vehicle weight by clicking HERE or visiting www.henkelna.com/lightenup. Follow us on Twitter @HenkelAuto_NA.