Powder coating is an environmentally friendly, cost-effective alternative to painting metal objects. Powder coatings are incredibly tough and long-lasting, providing years of protection from weather and wear. However, when an object that requires heat transfer to function properly, such as a heat sync or auto part, is powder coated, it may affect the item's overall performance.
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There are two general types of powder coating: thermoplastic and thermosetting. Thermoplastics are nylon-based coatings that exhibit excellent protective properties, but can melt back into their original state if exposed to enough heat. Thermosetting coatings, mainly epoxies, polyurethanes, polyesters and acrylics, do not have a tendency to revert to a liquid, because they undergo a chemical linking process when heated.
Basics of Heat Transfer
Heat is transferred from metals in one of three ways. Conduction occurs when heat is emitted by a metal object and warms the air around it -- this is the least efficient method of heat transfer in metals. Convection occurs when air passes over the heated object and carries some of the heat energy away with it. Radiation is a form of heat transfer that can occur without any input from the environment. Objects radiate excess wave energy into the environment around them, but the energy can continue on in a vacuum forever.
When aluminum is coated with a powder coating, it has essentially been insulated. A variety of factors influence how well the insulation is doing its job, but regardless, heat transfer is slowed. Since the plastic particles are between the aluminum and the environment, it is difficult for convection or radiation to take place at the same pace as with bare aluminum. Heat must transfer through the plastic first, which slows the process.
Maximizing Heat Transfer
If you wish to powder coat an item for which heat transfer is vital, there are some options. Make sure that you apply only the thinnest coat of material possible. This cuts down on the amount of insulation that heat has to pass through to escape. A variety of additives, such as metallic pigments, can be added to some powder coatings to help speed the process of heat transfer.