Sanhua has a mature process involving the application of trivalent chromium pretreatment (TCP) coating on microchannel heat exchangers (MCHEs), in the U.S. and Asian markets. All-aluminum MCHE coils are designed to use less refrigerant and facilitate better heat transfer but they face corrosion issues when unprotected. Sanhua will introduce TCP to the Chinese market during CRH 2017.
The TCP coating provides a chemical conversion layer on aluminum and aluminum alloy MCHE coils to protect against corrosive atmospheres. TCP coating is an easy-to-perform multi-step process that includes cleaning, passivating, and water rinsing. Complete immersion processes can ensure 100% coverage on the surface of the coil, forming an even and uniform film. The coating does not contain hexavalent chrome (Cr6+) or any other restricted hazardous substances. The TCP layer thickness is nanoscale, thus does not affect heat transfer or air flow.