Pros and Cons for Ambient Temp Pretreatment
Can you explain to me the pro’s and con’s of room-temperature-pretreatment?
Q. We powder coat sheet metal parts that are about 1/8-ft thick x 3-inches wide x 24-inches long. They have holes in them that we use for hanging on custom wire hooks from the overhead conveyor. The upstream processes leave light mineral oil, punch press oils and rust inhibitors. In addition there is a process upstream which brings the entire product up to about 200°F for about two seconds.
Our current pretreatment is a heated phosphoric acid three-tank system of acid, rinse and rinse.
I am in the process of replacing the system due to worn-out tanks and exhaust systems. In my research, I recently found a “room temperature” strategy for pretreatment. This is of very high interest for many reasons.
Can you explain to me the pro’s and con’s of room-temperature-pretreatment? D.O.
A. The obvious pro to the room temperature pretreatment is the energy savings related to decreased use of your utilities to heat one or more of the process tanks you mentioned.
The current system you mention used to clean oils and rust inhibitors would not be very effective if it did not contain surfactants for removal of the soils. A fully formulated alkaline cleaner may be more effective, but if you are getting adequate results with the current process, it leads me to believe that you either have oils that are very light and easily removed or that your cleanliness requirements are not very great.
Given that, a room temperature cleaning process may be worth looking into. Generally speaking, cleaning is more effective if done at elevated temperatures, however there are some products formulated to clean fairly well at lower temperatures. I would suggest not relying on only the one you have found in your research, but also investigate a couple competitors to evaluate not only how effective the chemistry is, but judge the total package, including tank life, waste products and service. Potential suppliers can be found online at www.pfonline.com.
Infrared cure is gaining increased attention from coaters as a result of shorter cure cycles and the possibility of smaller floor space requirements when compared to convection oven curing.
Powder coating is one of the most durable finishes that can be applied to industrial manufactured products, and offers excellent corrosion protection and is very safe because of its lack of volatile organic compounds.
Metal fabricators that laser-cut with oxygen take steps to prepare parts better for powder coating.