We have experienced some corrosion on tubular heat exchangers used for swimming pools. We tried to Teflon coat the coils but could not get a complete or uniform coating. Could electrocoat be the answer? G.A.
All types of heat exchangers are excellent candidates for electrocoat because it provides corrosion resistance. Even though the coating is an organic finish and has a thermal exchange coefficient of itself, the coating thickness can be controlled to a thin film that can be built into the design of the exchanger or will fall within the safety factor of the design. The completeness of the coating should eliminate corrosion moving to uncoated areas. All-tubular exchangers should be able to get a uniform coating on 100% of the surface, unless the tubes are wound or placed very tightly. Tube-to-tube contact must be avoided. Fin-and-tube exchangers (like radiators) require some special considerations to achieve uniform coating thickness, which will be covered next.
The design of all types of heat exchangers needs to be looked at before even having samples electrocoated. The following are design considerations:
If the design fits the above considerations, then the surface area to be coated is the next concern for electrocoating. Heat exchangers usually have a very high ratio of surface area (in ft2) to cubic area of the system design. Several equipment design consideration can be altered or adjusted to accommodate heat exchangers, if the system is not dedicated to heat exchangers. Some of those equipment design considerations are as follows:
Working with your equipment supplier or a consultant can help with these considerations. Most custom coaters have used some of these “tricks of the trade” to accommodate heat exchangers. An article on PF ONLINE talks about a shop that electrocoats heat exchangers. You can find it here.