Thinking About Powder Coating…

Question:

We manufacture custom welded aluminum gates and fencing. Perhaps you could provide me some information about powder coating processes, equipment needs and pricing. We currently are using an acid etch primer and latex paint process on our gates. We are considering switching to water-based Imron by Dupont. Most of the products that we manufacture are long and narrow. Our typical gate has a two-inch tubular frame and one-inch pickets on six-inch centers, leaving a large open space in between. Lengths of gate leaves vary from 4-18 ft. Heights are usually between 4-10 ft. We are a custom shop, in other words, each product is built to customers’ design specifications so we are not a production run shop.

Can you provide answers to the following questions?

Is powder coating the best solution to provide long-lasting superior finishes to our products?

How re-sistant is powder coating to Florida's environmental conditions (direct sun and salt spray)? What about fading, peeling and chalking?

We get requests for a large number of colors and occasionally faux finishes (two coats). Are there hundreds of color combinations available? What are the minimum batch sizes that can be purchased on custom colors?

What pretreatment would be required for the aluminum parts prior to coating? What environmental and disposal implications are there from the pretreatment and the waste powder?

What physical equipment is required to house the coating? How much space does it consume? Is there a “cold” process available for powder coating?

Should we consider building fluidized beds or spray wands to apply the powder for this shape?

As you can see, we are pure novices in regards to powder coating. Your answers are appreciated. J. B.

Answer:

You are asking the same questions that anyone looking at powder coating for the first time asks. Even though I have been answering these same questions for the last 23 years, I must caution you, and all my readers, “that a one size fits all” answer does not exist. However, here are the answers to your particular questions for your particular situation. I will use the same numbering system to eliminate repeating the questions in the answers.

Powder coatings have been the coatings of choice for your particular industry for the last 30 years. The fence and gate companies either perform the coating themselves or subcontract the service.
Powder coatings have been successfully tested to perform extremely well in Florida exposure tests. Some coatings have been tested for 3-5+ years without any noticeable loss in gloss or color. The outdoor furniture industry warrants its powder coated products for 20 years. These products see the same conditions, or worse, than yours would.
Powder coatings are available in the entire color spectrum and are available in faux finishes like hammertones, tinted clears, metallics and flamboyants. Powder coatings can be applied in multiple coats to obtain unique finishes, like marbling, veins, spatters, etc. Many powder companies offer same day shipment of stock colors. Some companies state they have more than 300 stock colors and formulations. The smallest batch size for any powder coating is three pounds, although most people buy them in 50 pound boxes.
Aluminum parts should at least be etched and cleaned before powder coating. Applying a pretreatment to enhance the coating life may also be desirable. A conversion coating or dried-in-place (DIP) pretreatment can extend the salt spray to 5,000 hours on aluminum parts. Most powder coatings (all powder coatings except those few formulations that contain heavy metals) can be disposed of without any special care as “landfill materials.” The conversion coating pretreatments, described previously, can present a problem; however, there are pretreatments that do not require special disposal precautions. Reviewing your coating requirements with a pretreatment chemical supplier will help to determine if you will have a problem.
Powder coating requires the following steps: cleaning, drying, spraying and curing. Each step requires unique equipment, although drying and curing can occur in the same device. The equipment size depends upon the size of your product and how many you must produce per unit of production time. From this information you can “right-size” your equipment and determine if a batch system or a conveyorized system is required. Floor space is determined after the equipment size has been determined. I suspect that your system production requirements will dictate that a batch system is best suited to your needs. Given that and your product size, a batch powder coating system should fit into a 60 x 60 ft room. There is no “cold” powder coating process available, but there are low temperature formulations available that can reduce the cure temperature to 250 F.
Your system should employ the use of spray equipment. Fluidized bed systems are normally used for functional coatings requiring heavy film builds.