Pulsing current and squared wavelength rectifier for anodizing aluminum

• Grant number: 99/06334-9
• Support Opportunities: Research Grants - Innovative Research in Small Business - PIPE
• Start date: April 01, 2000
• End date: August 31, 2001
• Field of knowledge: Engineering - Chemical Engineering - Industrial Operations and Equipment for Chemical Engineering
• Principal Investigator: Elisabete Jorge Pessine
• Grantee: Elisabete Jorge Pessine
• Company: Termocontroles Indústria e Comércio Ltda
• City: São Paulo

Abstract

The technological innovation proposed here, to be developed jointly by Termocontroles and Unicamp-Ipen (São Paulo State University - Campinas and the Institute of Nuclear and Energy Research), consists of the manufacturing of a pulsing current and high-power, squared wavelength rectifier appropriate to the hard anodization process to be used on an industrial scale. Anodization is one of the best methods of giving aluminum a protective coating. The hard anodization process permits thicker coating than the conventional ones. However, they are restricted by the composition of the aluminum alloys, by the temperature and by their degree of burning. High temperatures encourage the formation of an external soft and porous anodic layer, reducing resistance to wear and significantly limiting the increase in thickness. The advantages of anodizing aluminum alloys carried out using squared wavelength pulsing current rectifiers, compared with processes using only continuous current, range from a saving of 25 per cent in use of reagents, including the achievement of thicker layers (50 - 700 µm) faster, whilst obtaining a coating which is more resistant to corrosion and abrasion, since the layer is generally more homogeneous and less porous, without burning. In hard anodization of large aluminum parts the rectifier needs to be high powered, since the Al2O3 film is an electrical insulator. The feasibility of constructing a prototype will be established in the laboratory. (AU)