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Forming Protective Coatings on Magnesium Alloys

IP.com Disclosure Number: IPCOM000092328D
Original Publication Date: 1967-Dec-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Sekora, CM: AUTHOR

Abstract

The magnesium alloy part to be coated is first processed through a cleaning cycle comprising the successive steps of vapor degreasing, alkaline cleaning, and immersion in a dilute mineral acid bath. The part is then immersed in a room temperature aqueous solution of trisodium phosphate Na(3)PO(4).12H(2)O approximately 20% by weight. While immersed in this solution an electrical potential is applied to the part to form an anodized magnesium phosphate coating on the external surfaces. The magnitude of the voltage can be varied to control the thickness and rate of deposition of the coating. High-current densities are possible, but a phosphate film forms within a wide range of current densities.

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Forming Protective Coatings on Magnesium Alloys

The magnesium alloy part to be coated is first processed through a cleaning cycle comprising the successive steps of vapor degreasing, alkaline cleaning, and immersion in a dilute mineral acid bath. The part is then immersed in a room temperature aqueous solution of trisodium phosphate Na(3)PO(4).12H(2)O approximately 20% by weight. While immersed in this solution an electrical potential is applied to the part to form an anodized magnesium phosphate coating on the external surfaces. The magnitude of the voltage can be varied to control the thickness and rate of deposition of the coating. High-current densities are possible, but a phosphate film forms within a wide range of current densities. The process, which can be used with AC or DC source voltages is easy to control, is non-toxic, and involves a single component solution. Except those alloys containing lithium such as LA141, the ceramic-like coating is obtained on various magnesium alloys such as ZE-10, AZ-31, HM-21 and HK-31 to provide resistance against corrosion and abrasion. Optimum protection to the coated alloy part is readily obtained by applying an organic coating such as polyurathane.

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