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pfonline.com/experts 48 NOVEMBER 2015 — pfonline.com p f o n l i n e . c o m / e x p e r t s POWDER COATING C L I N I C RODGER TALBERT Consultant powdercoating@pfonline.com Post Forming of Powder Coated Parts Q. Is there any product/process to powder coat steel and roll form the steel without damaging the coating? I am working with a process where we want to form the top lips of a painted bucket around a lid. The bucket is similar to a regular garden water bucket in size and shape. The coating will need to take a force of 20 kN (kilonewton) during the forming process. Are there powders that can take that kind of stress? A. There are powders designed for post-forming. The only way to know if they will take the stress of your process is to try a sample. One challenge is the film thickness; if the film is too thick you will have a lot of trouble and you may not be able to control the film tightly enough. If the sample powder does not work, consider electrocoat. E-coat can be post-formed and the film can be controlled below 1 mil. Primer Options for Powder Q. We make steel cabinets used to house electrical devices such as audio and video equipment or communication devices. We use a single coat of hybrid powder for most of our products. Some of our customers are asking for superior corrosion resistance for when the cabinet is installed in buildings that have limited control of heat and humidity in a shop environment. They have seen rust near edges and inside corners. What type of primer would be best to enhance the corrosion resistance of our cabinets? A. Any primer or two-coat process should improve corrosion resistance. The "best" depends on how much additional protection you are trying to add. You could have the panels e-coated. E-coat is a high quality immersion primer that penetrates and provides overall coverage. A drawback is the cost and handling associated with sending parts to another coater. You could also use a powder primer. Powder primer is durable and can be enhanced with zinc content for the highest level of corrosion resistance. Adding another layer of powder will complicate your process and increase your cost, but it can be done in-house. If you have a batch system, I would use an epoxy powder primer. After the part is clean, apply the primer coat and put the part in the oven for a partial cure. Consult with the supplier on the appropriate amount of cure cycle. Bring the part out, enable it to cool and apply your topcoat. Put the part back in the oven for a full cure cycle. I would not use zinc primer. The corrosion protection may be better, but you will have more difficulty handling and applying the zinc-rich material. Also, zinc primers are most effective on a blasted steel surface and you most likely do not blast your panels. It is more difficult if your system is conveyorized. If there is space, install another booth for the primer and small infrared oven to provide a short cure cycle. To Reclaim or Not to Reclaim Q. We have a powder booth and cyclone recovery system capable of reclaiming colors for reuse. We're not sure how to determine whether or not to reclaim some of our colors. What method can we use to help us make that decision? A. The decision on whether or not to reclaim powder is based on a comparison of the value of the powder that can be reclaimed versus the investment required to reclaim it. The variables that you need to input are: • Ho w much powder will be over-sprayed into the recovery system? • What is the dollar value of the over- sprayed powder? • What is my cost in time and labor to reclaim the over-sprayed powder? For example, assume that the time in the color is around one hour. The system has eight automatic guns. The total amount of powder sprayed during the one hour run is 200 pounds and the transfer efficiency is 60 percent. The total powder sprayed into the recovery system is 80 pounds. The powder cost per pound is $2.50. The total value of the powder over-sprayed is $200. The system will take two people around 15 minutes to change from this color into the next color. Taking into account the fixed cost of the system (dollars required to support the system; rent, staff, building utilities, and so on) and the labor to make the change, the cost for that 15 minutes of downtime is around $150. Fixed cost varies a lot depending on the size of the facility and the business. Considering that you cannot make money on the line when it is down for color change, this comparison is close and it may not be a good value. Once you have done the math a couple of times you will understand how long you need to be in a high value color to justify the reclaim cost. Long runs of the same color are more attractive for reclaim than very short runs. Long runs of high value powder are the most attractive and very short runs of low value powder are the least attractive for reclaim. Corrosion Resistance Options Q. We have a chance to do a job that involves some large steel enclosures that will be used in an outdoor location near the seacoast. Most of the product we coat has modest require- ments for corrosion resistance, but this job will need a very tough film that will not break down in one of the toughest environments. We have a 5-stage iron phosphate washer and we are not sure that it will provide enough corrosion