Powder Coating at T & D Metal Manufacturing and Production

What is Powder Coating ? ...... Here is a great Powder Coating Article

What is powder coating, why should I consider using it, and how will it work in my operation are questions that every finisher needs to be asking today. Briefly, these questions can be answered as follows:

1) powder is a dry, clean finish that gives a highly durable coating,
2) in the long run, powder will save you money, and
3) a powder coating system can be designed to meet just about any requirement your operation may have.

The purpose of this page is to explain quickly and simply how powder coating delivers these highly desirable solutions to many finishing problems, and to provide you with a practical, worksheet approach, to help you decide if moving to powder is the right move for you.

Over the past decade powder coating has been increasingly accepted as the preferred finishing process for the future. The reasons for this conversion from wet to dry can be attributed to three major forces: economy — the high cost of energy and materials require a more cost effective and less wasteful process; excellence — consumers, and other end users, are demanding higher quality and more durable finishes; and ecology — progressively more stringent regulations are being aggressively enforced in an effort to control air pollution and hazardous waste disposal. Which in turn goes back to economy. The cost of complying with the Regulations and the disposal of toxic and flammable waste are constantly rising.

Many companies have found that it is less expensive to convert to powder than to bring their wet systems into compliance!

With strong financial arguments providing the necessary stimulus, therefore, powder coating technology has evolved quickly. The quality and variety of powders available have grown as an increasing number of companies get involved with its production; and the technology for spraying the powder, collecting it and reusing it, is constantly improving transfer efficiencies and material utilization, and reducing color change times. Early perceptions that powder was too difficult to control, too costly to install, too time consuming for color change, or did not provide enough choice of color are largely obsolete today.

But the move to a totally new technology can still be confusing. This page is designed to make your decision easier, providing both explanations and justifications to help determine the right solution for you. So let's start at the beginning and work through the questions.

What is Powder Coating?

Powder is a dry coating. Instead of being dissolved or suspended in a liquid medium, such as solvent or water, powder is applied in a granular form. This material is finer than ground pepper but coarser than flour, and is applied directly to the surface to be coated.

The powder is created by blending the various components (binders, resins, pigments, fillers and additives) and processing them through an extruder into a continuous mass. This homo-genous mass is cooled and broken into small chips, which are then ground into the powder. Each powder particle contains within it the necessary components for reforming into the finished coating. After the powder is applied to the part, typically using an electrostatic spray process, the part passes through an oven and cures, melting into a smooth film on the surface of the part.

Powder Formulation

There are two distinct types of powder, Thermoset and Thermoplastic. The Thermoset powders are reactive, which means that under cure conditions there is a chemical "crosslinking", so that, once cured, the coating will not remelt. Epoxies, acrylics and most hybrids are examples of Thermoset powders, making up over 90% of the current powder market.

Thermoplastic powders do not "crosslink" when cured, but simply melt and flow over the surface of the part. The film hardens on cooling, but if it is reheated it will remelt. Vinyls, nylons and fluorocarbons are examples of thermoplastic powders.

Enamel powder is a specialized formulation used in applications that previously used liquid porcelain enamel. It utilizes glass in its formulation and is cured, or fired, at a very high heat. The result is a finish that is particularly resistant to heat, scratching and harsh chemicals, and is typically used in appliances, such as washers, dryers, ovens and ranges.

How is the Powder Applied?

The application process involves applying a charge to the dry powder particles and spraying them onto a grounded substrate. The substrate, or part, is typically grounded through the conveyor or hanger holding the part. The powder, once attracted to the part, is then held on the surface until it is melted and cured into a smooth coating film in the bake oven. The spray process takes place inside a booth designed to contain the oversprayed powder and makes it possible to collect the overspray and ultimately reclaim it for reuse.

The powder is fed pneumatically out of the powder container, or hopper, into the powder applicator, or gun. As the powder exits the gun, a low amperage, high voltage charge is applied to the powder particles, causing them to be attracted to the grounded workpiece. This attraction may even cause the powder to "wrap" around the piece, coating the back side.

The oversprayed powder, suspended in the air contained inside the powder booth, is then passed through a separation process that permits the powder particles to be retrieved from the air. The clean air is fed back to the work environment, eliminating the need for air make-up. The reclaimed powder is mixed with a proportionate amount of fresh, virgin powder for reuse achieving consistent results and up to 98% material utilization.

Now that we have covered the basics you should have a better idea of what powder coating is all about.