Properties and pretreatment requirements of aluminum and its alloys

Aluminum is a soft, light metal that is highly ductile, malleable, and an excellent non-magnetic electricity conductor. Apart from steel aluminum is one of the top metals of choice and is widely used in the manufacturing industry. Alloying aluminum with different materials like zinc, lithium, magnesium, manganese, copper, or silicon can significantly adjust its properties for use in many different applications. Dependent on the composition and metallurgy, aluminum alloy components exhibit different microstructures and surfaces. But they have one thing in common, they form an ever-present natural oxide film covering the surface, which can prevent proper adhesion of subsequent coatings. Also, the oxide layer can vary in thickness and composition depending on the alloy type and processing conditions. Products fabricated from aluminum alloys behave differently and do not uniformly respond to various chemical and electrochemical treatments.

Atotech aluminum pretreatment solutions

Besides the contamination of the plating bath with manufacturing residues incorrectly performed pretreatment can lead to patchy or incomplete coating, poor bonding of a coating to the base material, pitting and blistering up to peel-off effects that can result in poor performance or low corrosion resistance of the final part.

Preparing parts made from aluminum alloys requires several pretreatment steps that provide thorough cleaning to remove oils, grease, smut, and oxides and to treat any surface modifications to create a uniform surface for the best quality of subsequent plating and coating layers.

Our pretreatment technologies optimally prepare aluminum parts for subsequent finishing operations like electroless and electrolytic plating and enhance its surface to ensure good adhesion and quality of the deposited metals. Our range of proven cleaners and pretreatment processes is designed to provide the best plating/coating quality over a long operating time and for diverse substrate materials.

Our product portfolio

UniClean® 151: Mild alkaline hot soak cleaner for steel, nonferrous metal, and aluminum, suitable for barrel and rack plating lines, exhibiting high cleaning power and receptivity, drawing oil and pigmentation contaminations. UniClean® 151 does not attack aluminum or aluminum alloys

UniClean® 1020: Highly alkaline etchant for aluminum and its alloys containing a special sequestrant that produces a highly specular etch providing a very decorative effect. UniClean® 1020 has a high capacity for the prevention of oxide scale formation

AlumEtch® series: Liquid etches formulated to deoxidize, desmut, and condition the surface of any aluminum alloy for subsequent processing exhibiting an aggressive etch rate and acting as an adhesion promoter for subsequent coating. AlumEtch® solutions are suitable for various aluminum pretreatment applications such as plating, painting, rubber bonding, anodizing, passivation, and other decorative and functional applications

AlumSeal® series: Highly uniform zinc coatings preventing oxide film formation and promoting excellent adhesion of subsequent metal deposits

AlumSeal® Activator BD: Highly stable solution for stripping initial zincate layer from aluminum, can be used as an alternative to nitric acid

AlumSeal® AD series: Products for sealing aluminum surfaces, including special products for conditioning and coloring prior to zincation or further processes achieving specific cosmetic appearance

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