Q. What material would you recommend for the chilling system that I need to install for my anodizing tank, which has a capacity of 1,800 L (475 gal)? Can I go for Type 316 stainless steel or copper pipe with lead plating? S.H.
A. There are a number of ways to design a cooling system for an anodizing tank. I have found that pumping the anodizing bath electrolyte through an external heat exchanger is by far the most effective and efficient method of maintaining an even temperature throughout the bath at the full heat load. This method removes the cooling coil from the anodizing tank and eliminates potential problems with both chemical corrosion and electrolytic corrosion of the cooling coil. It also prevents the possibility of either refrigerant (in the case of a direct-expansion coil system) or chilled water/glycol leaking into the bath from a hole in the coil.
With an external heat exchanger, it is possible to control the flow of the cooling medium, either the chilled water or cold glycol, to provide very precise bath-temperature control within a tight range, usually ±2°. Any leaks that might occur in the system over time would be outside the tank and, therefore, much easier to deal with. It also protects the anodizing bath from dilution and contamination. There are any number of ways to provide for containment and handling of acid or cooling solution leaks that inevitably will occur over time, no matter how well the system is designed and put together.