HARD COAT DETAILS
WE ARE DOING HARD ANODISING IN INDIA,WE NEED THE FOLLOWING DETAILS FROM ANY OF OUR EXPERTS.
1) WHICH IS THE BEST MATERIAL FOR CATHODE,ALUMINIUM OR LEAD IF IN CASE OF ALUMINIUM WHAT IS THE ADVANTAGES OF USING IT
2) WHICH MATERIAL IS TO BE USED FOR CHILLING PLANT COIL, WHICH IS IMMERSED IN SULFURIC AND OXALIC ACID MIX SOLUTION. WHEN WE USE LEAD COILS HOW IS THE PERFORMANCE OF COOLING CONDUCTIVITY OF LEAD.
3) OUR ELECTRICAL RECTIFIER IS GETTING VERY HIGH HEAT EVEN THOUGH IT IS OIL COOLED ONE, REASONS FOR THE SAME
4) ANY OTHER ACID CONCENTRATION WHICH WILL GIVE BETTER BLACK SHADE THAN SULFURIC AND OXALIC MIX IN HARD COAT.ELANGOVAN DAMODARAN
SRI BALAJI ENTERPRISES - INDIA
1). Both points of view are covered in Letter #1177 (even a third point of view that graphite is best!).
2). Many in the U.S. feel that gaseous refrigerant should not be run through the coils in an anodizing tank, but that there should be a primary refrigerant loop feeding an external heat exchanger, and a secondary chilled water loop feeding the anodizing tank. Lead is a metal, and although the thermal conductivity of metals varies widely, the 'U' factor for most metals doesn't vary by much, especially after applying a fouling factor.
3). I've never seen an oil-cooled rectifier; I guess they are more common in other countries than in the U.S.
4). Sorry, no personal expertise on this question.
Ted Mooney, P.E. RET
Pine Beach, New Jersey
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