Method for Passivating a Surface of a Metal Part

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This patent describes a method for passivating the surface of a metal part, particularly light metals such as aluminum or magnesium, by applying a calcium phosphate-based conversion coating that includes oxides, hydroxides, and carbonates from both the metal and the treatment solution. The innovative aspect is the use of a passivation (conversion) solution containing at least one chelating agent, such as an organic acid, amino acid, or vitamin. This approach results in a significantly improved, nearly crack-free protective layer, as the use of specific chelating agents enables controlled and uniform layer formation, enhancing corrosion resistance.

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• Corrosion protection for automotive components (body structures, inner/outer parts, chassis, seat frames) made from aluminum, magnesium, or their alloys.
• Protection of metal parts in consumer electronics and appliances which incorporate light metal parts.
• Medical device manufacturing, where corrosion-resistant and biocompatible coatings on implants or surgical tools are required.
• Aerospace parts that require lightweight and corrosion-resistant coatings.
• General industrial applications where metal parts are exposed to corrosion risk and require durable passivation layers.

BenefitsContent extracted from patent full text and abstract with AI.

• Improved corrosion resistance compared to prior methods, especially against contact corrosion and filiform corrosion.
• Formation of a closed, crack-free coating that enhances protection and durability.
• Simplified and more controllable process due to the use of a specific chelating agent, rather than a complex mixture.
• The protective layer maintains sufficient electrical conductivity, which is beneficial during subsequent coating or painting processes.
• Applicable to a wide range of metals, especially lightweight alloys (aluminum, magnesium), broadening its utility across different industries.
• Potential for use in various coating system sequences, e.g., as a base layer for further organic coatings (KTL, powder coating, paints).
• The coating process can be tuned to operate at neutral or acidic pH, providing flexibility depending on requirements.

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Patent Abstract

The invention relates to a method for passivating a surface (25) of a metal part (3), wherein a calcium phosphate-containing conversion coating (5) that comprises oxides and hydroxides as well as carbonates of the material from the metal part, is created on the surface (25) in a passivation step using an aqueous passivation solution. According to the invention, the passivation solution for forming the conversion coating (5) includes at least one substance that acts as a chelating agent.