Issue link: https://www.e-digitaleditions.com/i/727416
POWDER COATING, September 2016 39 By popular demand, we're bringing you a series of past pretreatment problem columns, representing the best of Brad B. Gruss, our columnist for more than 20 years, who has retired as president of the consulting firm, Pretreatment & Process Consulting LLC. Brad specialized in training, troubleshooting, and indepen- dent line audits for pretreatment processes. In his more than 30 years in the industry, he made numerous presentations on pre- treatment for powder coating. Blasting problems Problem I don't know if you can answer my question or not about blast- ing. We have a 70/30 mixture, 70 shot, and 30 grit. We manufacture grill guards and run them through a blaster to clean before going to the paint shop, removing oil and grime and so on. We have to run the grill guards through the blaster twice because the blaster doesn't get the rust completely off. We're running the track at 7 feet, 7 inches per minute. We're going to slow down the track to see if that helps. Any other suggestions that may help us? M.K., Dallas, Tex. Solution You've left out some important information, but you nail it on the fact that you know all the rust, scale, and debris should be removed. Here are a couple of items for you to look into. Yes, slow down your line speed to see if you indeed can remove the rust by using longer contact time. Some man- ufacturers have the option to do a two- stage blast. The first stage is a coarse blast, and the second is a refining blast to control mil profile. Not all metal finishers have that luxury. If the addi- tional contact time doesn't solve the issue, look at a change in media to a more aggressive blast. Check with your media supplier for a change or a differ- ent ratio of media. A very important aspect of blasting is the remaining profile height. Powder coaters who blast should always use a profilometer to measure blast profile. Brad B. Gruss Pretreatment & Process Consulting LLC BEST OF PRETREATMENT PROBLEM SOLVER Require quic ck turn around ime on die c d time on die c u uts and molded parts ? ed parts e e hav W ered e you cov . CUSTOM F .customfabricate.com www.customfabricate.com • info@customfabricate.com e . Oakwood Park Driv 5500 W W. Oakwood Park Driv y FABRICATIN • info@customfabricate.com ranklin, WI 53132 • 800-556-71 e, F NG & SUPPLI 188 IES