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must be stored and used in an envi- ronmentally controlled room. Even if the cost to convert to powder coating is higher initially, payback and return on investment (ROI) favors powder coating because of its lower operational cost when com- pared with liquid coating. This fact has been proved in many installa- tions in North America; some compa- nies have experienced 2, or less, years' payback (more than 50 percent ROI). Very few investments can guarantee that high a yield. Myth #2: Powder coatings are difficult to apply. Powder coatings require a slightly different manual application tech- nique than liquid paints. With liquid paints, often the gun is triggered on and off with each pass to prevent runs. Each pass by the sprayer must be made fast to reduce runs or sags. Powder coatings, on the other hand, should be applied in slow, deliberate gun motions without triggering on/off. This ensures that the powder is properly charged and deposited evenly on the surface. Because of their formulation properties, powder coatings are extremely resistant to runs and sags at film builds up to 8.0 mils thick. In fact, powder coatings are so easy to apply that most com- panies have difficulty preventing manual sprayers from applying too much powder on their parts. This brings us to our next myth. Myth #3: Powder coatings are applied too thick. Powder coatings have a reputation for being thick coatings. True, pow- der coatings are normally applied in the 1.5- to 3.0-mil range compared with liquids applied in the 0.5- to 1.5- mil range. But this is normally due to operator error than anything else. Powder coatings have been success- fully controlled in many applications to 1.5 mils (±0.2 mil). Most people are too lazy to implement the process control or to maintain the equipment to ensure this level of control. And because powder coatings are so cheap, they would rather write-off the additional coating expense than implement the controls required to maintain a tighter film thickness. This fact is further reinforced because of powder coating's resis- tance to runs and sags. Frankly, heavily coated parts are always acceptable (except when the coating is so thick that you can't assemble the components), and light coverage sometimes requires re-coating. So, most people err on the heavy side. Myth #4: Color change is difficult with powder coatings. This myth always bothered me. Peo- ple look at minutes to change liquid colors, which normally require flush- ing the guns with solvent and con- necting a new pressure pot. Well, powder guns can be cleaned just as easily by flushing with compressed air and changing powder hoppers (or the powder box when using box- feeder equipment). The real problem occurs when the powder coating is reclaimed for reuse. In these systems, the reclaim equipment must either be cleaned or be changed to get ready for the next color (reclaim is obvi- ously a benefit for powder coating), taking 15 minutes to 1 1 /2 hours, depending upon the size and amount of reclaim equipment. This may seem ridiculously long for a color change, but if you reclaim sufficient over- spray powder to justify the effort, then you gain the benefit of reduced operating cost. Most people have difficulty in deter- mining which colors they should reclaim and often reclaim colors that aren't economically justified. It's then that they complain that it takes 1 hour to change a color they're spray- ing for only 10 minutes. But look at the reasoning these people use: "Because powder coatings allow you to reclaim, you should reclaim every color." If you sprayed liquid paints before without the possibility of reclaiming, why would you collect every powder color for reuse? Pow- der should be reclaimed only if it's economically justified. If you follow this rule, the time and cost for color change will be offset by the value of the reclaimed powder. If it doesn't, then scrap the powder overspray as you would with liquid paints. MYTHBUSTERS Five common myths preventing liquid-to-powder conversions Myth #1: It's too expensive to convert to powder coating. Complete systems, including pre- treatment, ovens, spray booths, and guns, cost nearly the same for either liquid coating or powder coating. This fact is undisputed. However, when you're converting an existing liquid system to powder coating, you'll need to replace or retrofit the spray booth. Also, in some cases, the existing liq- uid system's pretreatment equipment or cure oven can't support the demands of powder coating. The best way to determine if the existing pretreatment equipment can be used for a powder coating pro- cess is to do a water-break-free test 1 on parts as they exit the pretreat equipment. If the parts pass this test, then the equipment can be used. Most times a change in pretreatment chemical strength or formulation will improve this process sufficiently to accommodate the cleanliness require- ments of the powder coating process. Cure ovens used in a powder coating process must provide the time at metal temperature to properly cure the powder coating. Each powder coating formulation has its own time- at-temperature requirements, but most powder cure requirements are both longer and hotter than typical liquid paints. Verification of your spe- cific oven should be made by the pow- der coating supplier. If the supplier approves the oven, then you're in luck. If not, you can add an infrared booster as a very quick and easy way to gain the metal temperature in the reduced dwell time of your existing oven. Fur- thermore, low temperature cure pow- der coating formulations can be an additional method of accommodating your existing cure oven. These mate- rials can be fully cured at lower oven temperatures or in shorter dwell times than standard powder coatings. However, these materials may not have the high performance properties your product may need, and they POWDER COATING, December 2016 29 POWDER COATING OVERVIEW