Coating With Powder

Over the last several years, our shop has come to depend on local contractors to reduce a lot of the painting duties we used to handle in-house. But, these contractors don’t actually paint our sign frames, letters and other metal objects; they powder-coat them. In fact, we have seen the amount of this type of service we use increase every year. And this trend isn’t unique to the sign business. The whole world of metal fabrication seems to be moving in that direction. Hmm... maybe this is a process we need to know more about.

With that in mind, back in November, my two sons and I went to the Nashville area to take a weekend hands-on school offered by Powder-X, a company that manufactures and sells powder coating equipment. And we learned a lot. So, for this month’s “Shop Talk”, I thought I’d share a little of our experiences that weekend, and take a closer look at the process of powder-coating and the benefits it offers to the sign business, and other businesses as well.

ALMOST MAGIC

Joey Golliver, a very likeable fellow from Alabama, and president of Powder-X, was our instructor that weekend. The very first thing he did was to explain the basics of how this process, which has been around for thirty years or so, actually works.

First, the powder itself, though not magic, is certainly a specialized product of modern technology. Ground very finely (like face powder), from specially formulated plastic polymers, the powder is made in two main variations: Thermoplastic powder, primarily used for corrosion resistant coatings, and Thermoset powders, used for decorative and protective finishes, the type used for coating metal sign components.

Thermoplastic powders are sprayed onto pre-heated metal and built up to a heavy coating of 10 to 15mils, to make corrosion proof coating for buried pipelines and other metal parts subject to corrosion. These powders are made “plastic” by heat, cure nearly instantly, but can be re-plasticized by applying heat again.

Thermoset powders, like the ones we used, are sprayed onto cold metals, and temporarily bonded to them by a static electric charge put into the powder by the spray gun used, and then the coated metal is heated in an oven to first liquefy the powder and then cure it to a hard and durable finish. These powders come in many beautiful standard colors, metallics, fluorescents, and even different surface finishes from a high gloss to flat or even textured finishes.

A lot of the sign items we have had coated over the past few years have been satin black in color, which works great for sign frames and the like, but the letters and other cut-outs we’ve done have been in a variety of colors. We’ve even had a few entire backgrounds of unfinished aluminum powder coated. And, the finish is harder and more durable than anything we could paint on (vinyl graphics bond fine to it as well, if the finish is satin or glossier.)

A SIMPLE PROCESS

As we learned hands-on at Powder-X that weekend, the process of coating metals with thermoset powders is fairly simple. Clean metal objects to be coated are hung from metal hooks on a rolling rack, and sprayed in a back draft spray booth with a low air pressure gun that mists the powder onto the metal parts. The rolling rack, and the parts hung from it, are connected to a ground wire, and the positively charged powder will automatically seek a ground by finding a bare spot on the metal.

The spray technique is very simple since the laws of physics are working for you. And, though it is possible to not spray enough powder to cover an object completely, it is hard to apply too heavy a coat because once the surface is completely covered with powder; the excess cannot find a ground and merely falls off.

The rack, with its coated products, is rolled off to the oven for a curing process that takes about 15 minutes at 400 degrees Fahrenheit. Clear coats can be added as a second step, and cured in the same way for a “candy-apple” or wet-look gloss.

Sloan, Slade and I took turns with other students that weekend to coat an odd assortment of metal objects, some of which we salvaged from a local wrecking yard. We used colors that varied from fluorescent safety orange to chartreuse, and even a fairly nice looking simulated chrome. It is fortunate, especially for sign makers, that powder-coating products come in such a wide variety of colors. But, a note of warning: mixing powders may or may not produce the same results that you would get with mixing paint.

Now, the actual spraying of the powders, and running things through an oven, and seeing the beautiful results this usually produces, was a lot of fun and not really hard work. Where a lot of the work comes in is in the first step of cleaning the metal objects to be coated. Oils and other contamination will affect, and even ruin the finished appearance and integrity of the coating. And the work to strip the job and re-coat it, is something to avoid at all costs.

SURFACE PREPARATION ROUTINE

Of course, most items powder-coated for sign making are made from new metal, and are not going to be as contaminated as someone’s antique auto parts. But, even new metals have manufacturing or protective oils on them (especially steel tubing), and are not really clean. So, a thorough surface preparation routine is critically important.

It was interesting to see what a few minutes of 400-degree heat would do to contaminated metals. Some of the parts we played with, fresh from the auto salvage yard, literally sweated oil even after what we thought was a good cleaning. Some metals, especially cast metals, can absorb a lot of oil, and will give it back slowly but surely when heated up for a while. This can be a time wasting disaster if you are powder coating it. Thankfully, as I had mentioned before, sign makers almost always work with new metals which are not likely to be very contaminated, and require only a bit of cleaning before the process of coating it can begin.

Our parts which we played with that weekend, besides some troubled oil soaked gears, turned out very nice and were very little trouble to work on. One large timing gear I did was finished in a chrome-look powder, and except for some scratches from a previous hard life, turned out very beautiful. I can see that finish being very useful when doing certain plate letter jobs. Other parts were done in various finishes, some of which are shown in the accompanying photos.

In the real world, that is the sign making world for us, we have used a variety of beautiful colors for letters, even including a metallic gold. We’ve coated complete lighted sign cabinets in gloss white, which will resist rust for years even in that damp environment, and lots of black sign frames, but also some welded steel frames done in green, blue and so forth.

POWDER SET-UP COSTS

With so much practical usage for powder coating in the sign business, what would it take to actually be able to do this step in-house? Well, we wanted to know that answer too, and here are some rough estimates.

A medium sized spray booth, say 8’ x 10’, x 16’ or so, would cost around $8,000-$9,000. The natural gas fired oven of equivalent size would cost about $21,000-$24,000. The industrial quality gun cost around $4,500, and racks, powder, and so forth would add some costs to the bill. So, for roughly $35,000 to $40,000 in initial cash outlay, one could go into the powder-coating business. But, it would also require around 1,500 to 2,000 square feet of dedicated shop space, which may be the hardest part to justify for a commercial sign business.

However, the demand is great and growing, so for some sign company entrepreneurs who wish to branch out a bit, the opportunity is certainly out there. But for most of us, the important thing to know is that in most areas there are reliable and reasonable powder coating contractors which will do a good job of providing a high quality outdoor finish for our sign projects that is not only better than paint, but less toxic to us and to the environment (one of the real reasons powder-coating was developed to begin with).

Working with a powder-coating service can free up our shop labor and shop space so we can produce more signs, while we give our customers a better and longer lasting product for their money. This can be a win-win situation for everyone involved. So far, that’s exactly how things have worked for us as we continue to incorporate more of these industrial quality finishes in our sign work each year. But, we look forward to the day when we can incorporate this process into our own sign making capabilities.