Aluminum Finishing Anodizing Process: Cost Efficiency and Sustainability

| Editor: Nicole Kareta

In addition to conversion processes, Henkel is also developing new Bonderite products for the three main steps of the anodizing process - degreasing, pickling and hot or cold sealing - one of the most common technologies for aluminum finishing.

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"With the increasing demand for lightweight and aesthetic aluminum parts, manufacturers need cost-effective anodizing processes to maximize the productivity and sustainability of their processes."
(Source: Henkel)

In its raw, unprocessed state, aluminum reacts with oxygen from the ambient air. During this so-called self-passivation process, an unaesthetic oxide layer forms, which grows uncontrollably depending on the influence of the weather. The anodizing process, on the other hand, transforms the outermost aluminum layer into a controlled thin and smooth oxide skin, which reliably protects the surface from further oxidation (corrosion). Depending on the specific requirements of the end product, the typical thickness of the anodized layer is normally between 5 and 25 µm.

"In view of the growing demand for lightweight and aesthetic aluminum parts, manufacturers need cost-effective anodizing processes to maximize the productivity and sustainability of their processes," says Raul Hernandez, Business Development Manager Light Metal Finishing at Henkel. "Our Bonderite portfolio for anodizing includes specialty products for all process steps, starting with cooling lubricants for mechanical processing, degreasing, pickling, decapering, brightening, anodizing, electrolytic coloring and densification. The range is led by a new one-component degreaser for e.g. highly polished parts that does not attack the surface, a long-term pickling additive for an excellent E6 surface, a highly effective hot sealing additive and a nickel-free cold sealing additive.

The anodizing process always starts with cleaning the parts. Henkel has developed Bonderite C-AK 62115 for brightened or high-gloss decorative parts that must not be stained before anodizing. The aluminum surface is not attacked during cleaning, even stubborn polishing paste residues are reliably removed and handling is easier with this one-component product than with two-component products.

As a supplier of products for long-term pickling, Henkel is known for its pickling additives and ready-to-use long-term pickling products from the Bonderite C-AK product family, which is characterized by low chemical consumption and high E6 pickling quality. With the E6 pickling, surface defects, such as drawing grooves, are eliminated by removing part of the material. The levelling of the surface during the pickling process also produces a uniform matt and very aesthetic finish. Bonderite C-AK 62250 is one of the company's latest product solutions in this field. It meets the high quality requirements for pickling performance and surface quality with simultaneously optimized process properties such as excellent bath stability, foam-free pickling and reduced carry-over of bath solution. Overall, the process is therefore very economical.

The last step in the anodizing process is densification. Here Henkel offers solutions for hot sealing and cold sealing with reduced toxicity:

Bonderite M-ED 11011 is Henkel's latest hot compaction additive designed to at least double the standard service life of sealed parts and increase the productivity of single-stage hot compaction by at least 20 %. Hot compaction with this product takes a maximum of 3 min./μm. By reducing the amount of solution required for the bath by 50 % or more, the solution also results in a smaller carbon footprint. Overall, Bonderite M-ED 11011 enables high cost savings per square meter of hot-compacted material.

Bonderite M-ED 11150/11151 offers a compacting solution for anodized aluminum. Although cold compaction can involve several steps, the process is a highly productive alternative to hot compaction, but is traditionally associated with nickel and the resulting toxicity problems. The new cold compaction additives from Henkel are completely nickel-free without affecting process time or compaction quality.

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