The surface of the metal should be cleaned for painting or covering with a thin layer of metal to protect it from wear and corrosion, and also aesthetic purposes. Almost all treatments involve fluids that require heating or cooling. Depending on the material, there are various treatment and coating methods. However, at first all metals are washed and degreased. Surface treatment typically include heating different process fluids in a number of vessels. This means that several heat exchangers are needed and, (in many cases) there is a need for utility coolers. Typically, a pump circulates the process fluid through heat exchanger, which uses a cooling fluid (usually water). Then the cooling medium itself is cooled by a chiller or radiator or both. The size of heat exchanger is often based on the heat, generated in the vessel fluid. The most common type of heat exchanger used in surface treatment is a simple coil. But it is often recommended to replace the coils in the fluid with external plate heat exchangers. The benefits include:
• Need less fluid volume and smaller tank
• There is no risk of damage to the coil when objects move up and down in the tank
• Fluid recirculation cause a turbulence that reduces or eliminates the need for a mixer
• easier maintenance
• The use of the standby unit is possible (for service and downtime)
Adjusting the temperature is a key factor in surface treatment (and heat treatment). Cost-effective solutions often require a combination of cooling and heating technologies (depending on ambient temperature).