Think Outside the (Hot) Box

By Sharon Spielman

If you have ever installed a powder coated part only to have a piece of the coating chip off during shipping or installation, you know that until now liquid touchup paint has been the fix.

What if you could touch up your powder coated part with actual powder coating in the field? Or, what if you wanted to powder coat a part that was not able to be disassembled and shipped to a shop? Butte, Mont.- based Resodyn Engineered Polymeric Systems Inc., has developed ResoCoat™ powder materials, which are specifically engineered for use with the company’s polymer thermal spray (PTS) systems to provide lower cure temperatures and radically reduced cure cycle times. According to Kevin Lane, director at Resodyn, all of these materials reach their peak performance properties during the application process, so they are immediately ready to be placed into service as soon as they are cool, literally in minutes. He says that with this advancement comes the ability to coat virtually any surface in the shop, manufacturing facility or at the installation job site. The total system also allows powder coatings to be repaired without removing the part from service using equiva- lent material, thereby eliminating the need to strip and recoat for minor damage.

The company currently offers polyester and polyester-urethane ResoCoat thermoset powder coatings, in addition to its family of ResoCoat thermoplastic coating powders. Knowing these powder coatings will be applied in the field and at locations that are far less than sterile, Lane says the company designed the coatings to be robust and user friendly through a range of application environments. “These coating formulations require only degrease and grit blast surface preparation and are intentionally resistant to contaminate-caused fisheye surface defects. The materi- als are designed for use in a broad range of applications across many different industries,” he says. All of these materials were developed to the exacting standards of Mil-Spec or the company’s client application specifications, and were subjected to a comprehensive battery of testing and qualification in accordance with ASTM and Mil-Spec standards. The coating development process is complete only after extensive testing to determine that each individual property of the finished coating meets requirements, says Lane. All formulations are exposed to a minimum of 2,000 hours ASTM Salt Fog testing as a normal development tool to fine tune corrosion resistance properties, with ongoing testing of the final commercial formulations.

The Benefits

These new polyester powders are engineered to be flexible to improve their durability and resistance to impact-caused defects. The three test panels shown in the picture were coated with ResoCoat TS-962 polyester powder using the PTS process to apply and cure the material. Forward and reverse 1⁄2" dia. ball impact of 160 in/lbs force, bending around a tapered mandrel down to 1⁄8" dia., and repeated flexing and bending of the coated thin aluminum passed adhesion. Lane says that Resodyn’s answer to stop- ping corrosion is to keep the coating surface intact and in place.

Reparability is another benefit. Lane says that Resodyn is not aware of any other process that can repair thermoset powder coatings in place with equivalent material. “This capability alone will enable cost savings and process improvement for industries such as the large shipyards building U.S. Navy vessels that are now incorporating powder coatings at an ever-accelerating rate to combat the effects of corrosion,” Lane says. Powder coated parts and components are now capable of being touched up after they are installed. Bolts, fasteners, welds and other features can be newly coated, and installation-caused damage can be repaired using powder coating instead of attempting to match the surface with wet paint repairs. The U.S. Navy currently uses powder coating as the premier, long-lasting finish for many large components and features on their ships such as watertight doors, louvers and metal furniture. Sometimes, damage to the coated surface is reported to occur during transport and installation, which requires cosmetic repair. These repairs currently are performed using wet paints, or the component is removed from service for strip and recoat. Addressing these issues with the PTS coating system will make in-service coating maintenance a routine matter and will eliminate the need for “Wet Paint” signs.

The Equipment

Lane explains that the enabling aspect of the “total solution” is the polymer thermal spray (PTS) equipment technology that the company has developed over the last decade and is currently introducing to the commercial market. This patents-pending technology uses only heated air, fully adjustable up to 1,296°F (700°C), to deposit and process the proprietary powder coating materials.

“Resodyn understood from the onset of equipment development that polymers degrade rapidly when they interact with open flame, so the PTS specification was always a ‘flameless’ heat source to thermally process the polymeric powders,” Lane says. The powder is introduced into the hot air path safely beyond the heat source and is gently heated and deposited onto the surface where it continues to flow into a complete, fully cured coating. Resodyn states that pure white coatings are possible with these systems with no microscopic evidence of burned particles in the finished coating.

Of interest to the oil and gas pipeline industry is the ability to apply polypropylene powder without any of the embrittlement issues caused by traditional flame spray processes. “This enables the application of the industry-preferred three-layer field joint coatings utilizing a fusion bonded epoxy base coat, tie-coat, and either polypropylene or polyethylene top coats with all three components applied with the PTS system in a seamless process,” he says.

The extensive technology development program under NASA and DoD sponsorship resulted in a family of commercial PTS systems that range in output capacity up to 30 kW of thermal energy. All of these PTS systems are designed to be completely portable, or can readily be adapted to machine mount or robotic manipulators for incorporation into continuous duty manufacturing processes.

All the systems will apply and cure the proprietary powder coating materials, so system selection will depend on the coating application and the required coating deposition rate. The smallest, most portable system is the PTS-2, which is actually worn by the operator. This 110 VAC, all-electric system is suitable for spot repair and coating small areas. “With a deposition pattern size of approximately a nickel, it really can be thought of as an air brush for powder coating,” Lane says. The PTS-5 and PTS-15 are also all electric systems, operating from a 220 VAC powder source. These systems have a thermal output of 5 kW and 15 kW respectively, and provide a well-defined spray deposition pattern.

The PTS-30 system is a high-output propane/air combustion powered system that utilizes Resodyn’s patented and patent pending “flameless” design to ensure that only heated air contacts the polymer particles throughout the coating process. The applicator gun design locks the flame onto the burner plate, similar to the operation of a lantern mantle, so that only a column of very hot air exits the front of the applicator. The powder particles, protected by an internally cooled feed tube, are injected into the center of the hot air column and onto the surface to be coated.

With its simplified controls, electronic spark ignition, and fluidized bed powder feed system, the PTS- 30 is easy to operate, and the necessary coating application skills can be learned with only a few hours of use by the operator, Lane explains. He equates using the PTS systems to that of operating a paint spray system. “You wouldn’t hand a high-quality paint spray gun to someone that has never sprayed and send them to paint your new car. But with a few hours of training and some practice, the skills required to make beautiful PTSapplied ResoCoat powder coatings quickly become second nature.”

Future Usage

In addition to commercial-use coatings, Lane says that Resodyn currently is working on development projects for the Department of Defense and other governmental agencies. In answer to a request from a U.S. Navy research facility, the company developed a PTS applied thermal and fire resistant coating for Navy bombs that allow time for personnel to extinguish shipboard fires and/or remove the ordnance to a safe area before fire-caused detonation occurs. The new coating is in the final stages of testing, and is intended to replace the currently used, 40- year-old version that contains undesirable components.

Other contracts include the development of a highway barrier coating for the U.S. Department of Transportation to prevent tire climb induced vehicle roll-overs; C-130 aircraft skid coating for the U.S. Air Force to reduce friction and wear during take-off and landing in Artic regions; and a contract with the U.S. Navy to develop a PTS repair coating and application process for Navy ship radar structures.

Sharon Spielman is editor of Powder Coated Tough magazine. She can be reached via email at sspielman@powdercoating.org. For more information on Resodyn Engineered Polymeric Systems Inc., visit www.resodyncoatings.com.