Heating and Cooling Systems
Choose the correct heating/cooling equipment for anodizing processes
In all anodizing industries, chemical tanks should be equipped with a suitable thermostatically controlled heating/cooling device for the anodizing solution (bath). It is essential since solution temperature affects many finishing factors, such as rates of deposition, activation, corrosion resistance and the ability of deposits to adhere to surfaces.
Sulfuric acid anodizing tank generates heat and requires cooling to maintain constant temperature. Sometimes cooling is also needed for phosphoric acid anodizing. On the opposite, other processes require heating. For example, cleaners, etches, dyes and seals may necessitate higher temperatures. Moreover, chemical tanks like chromic acid anodizing tanks need to be heated at start up and shops in cold climate naturally need to heat up their tanks at start up.
Steam coils are the most common heating method. It can be used in virtually any system and are easy to repair and replace. The use of steam or hot water flowing within the tubes of the exchanger will transfer heat from your source to the liquid within the tank. Temperature control is obtained by controlling the flow of liquid through the heat exchanger .Titanium Coils may serve double duty by heating with steam or hot water and cooling with cold water as required.
Immersed electric heaters are most efficient and less costly to buy and install. They are preferred for smaller tanks. Direct-fired burners are cheaper to maintain, but take up more tank space. They are often used on plating lines but can be used for anodizing tanks up to 40 ft long.
External exchangers are typically used by large-scale anodizing systems where in-tank space is major concern. Such equipment requires a pump to circulate corrosive liquids from the process tank through the exchanger and back to the tank. Shell-and-Tube and plate-and-frame are the most common styles.
Another decision is upon material of construction, of which numerous choices are available, such as steel, stainless steel, titanium, zicronium, nickel alloys, plastics, graphite, columbium, and tantalum. Selection depends on the best combination of economy and performance. Since titanium does not corrode in acid bath, many times it’s the preferred material for cooling/heating coils.