New polymeric coatings for cold forming

Louise Smyth

Henkel Adhesive Technologies has sharpened the market fit of its Bonderite L-FM FL portfolio of polymeric coatings for the surface conversion of metals used in cold forming operations. The optimized Bonderite L-FM FL process reduces the number of treatment steps from as much as ten to one or two and is fast emerging as an attractive alternative in the production of high-performance automotive bolts and screws.

Medium carbon or alloy steel grades designed for cold formed threaded fasteners in property classes such as 8.8., 9.8, 10.9 and 12.9 to require a prior surface conversion process to create a thin, adherent coating that will facilitate deformation and ensure the high quality of the final products. In the automotive industry, these cold formed screws and bolts are used in a wide range of engine, powertrain, suspension, wells and other demanding applications.

Traditional zinc phosphating and reactive soap processes, although well established in metal pretreatment for cold deformation, are associated with a number of potential drawbacks, including high acidity as well as high energy consumption and phosphate sludge. Moreover, they can involve up to ten individual steps, from initial degreasing and pickling to activation, phosphating and soaping with frequent intermediate rinsing.

“With Bonderite L-FM FL, Henkel has developed an innovative solution to all these challenges that provides a flexible one-step process with superior cost performances, reduced CO₂ impact and a much smaller water footprint,” says Emilio Bucci, Henkel’s Business Development Manager for Cold Forming in Europe.

Bonderite L-FM FL is a non-reactive, water-based polymeric coating that enables a sustainable surface conversion process. Since the coating adheres to the surface physically without any reaction, the only evaporates produced in the subsequent drying step prior to cold deformation are aqueous. As a one-step process, Bonderite L-FM FL eliminates all rinsing steps, which saves water, and also has a reduced energy demand with appropriately lower CO₂ emissions. Furthermore, when the cold formed screws are dephosphatized for final heat treatment, the polymeric coating is easier to remove, which permits the use of a dephosphating cleaner in much lower concentration, which means less consumption.


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