Hello Joe,
We currently use 1K paint on OEM parts and are planning to build a mini-line to paint powder on class A parts

Hello Joe,

We currently use 1K paint on OEM parts and are planning to build a mini-line to paint powder on class A parts. The size of the booth we want is 3 ft square with a line speed of 2 fpm, running 16 hours per day. How do we build a booth and collection system to capture powder overspray?

Khem Ramsaran, Paintline - Rollstamp Manufacturing

Greetings Khem,

It sounds like you need a “starter-kit” application booth to allow you to enter powder technology.

To construct one yourself, you will need a box-like structure to act as a target for the oversprayed powder. This can be built with plastic. Clear polycarbonate works well but is expensive; high-density polyethylene can also be used. Alternately, you can have your local tinman fabricate a sheet metal box. The box should be tapered in the back leading to a 3 or 4 in. duct flange. Booth illumination is recommended. A window can be fashioned in the sheet metal or opaque plastic, if used. Clear polycarbonate has obvious advantages for light distribution.

The working component of the booth is a dust collector. This can be purchased either new or used, if you would like to be frugal. I would recommend a small unit that has a minimum of 300 cfm capacity. There are a number of used equipment suppliers that offer these. I would check the websites of Federal Equipment, Aaron Equipment, Ingalls Equipment, Arnold Equipment and HGR Equipment.

The dust collector will have to be connected to the booth with suitably sized piping that is available from your local hardware supplier. I recommend industrial quality ductwork as opposed to residential heating piping. Ductwork and clamps can be ordered from McMaster-Carr and Grainger catalogs if a local source is not available.

These guidelines will allow you to design a spray-to-waste process. If you want to capture and recycle the oversprayed powder, you will need a more sophisticated system from a booth manufacturer. Companies such as Nordson, ITW-Gema, Wagner, Parker Ionics and Deimco can provide an off-the-shelf unit to meet your needs.

Dear Joe,

I have a customer who has pulled steel parts from various areas of the racks to test three colors for salt spray. All colors passed in an earlier salt spray test, but one color failed in the recent test. Film thickness and methyl ethyl ketone (MEK) testing showed the part to be okay. I have explained to the customer that the product will pass if it is pretreated properly, has the correct film thickness and is cured correctly. How would you convince the customer that the powder is okay?

Salt Spray

Dear Salty,

Your customer is wise to test powders on parts pulled from his pretreatment line. In doing so, he not only tests the powders in real-world conditions as opposed to idealized lab conditions (e.g., using Bonderite® panels), but also measures how well his pretreatment system is performing. You are wise to measure the film thickness and solvent resistance to verify that the powder has been applied and cured correctly.

If the powder demonstrates acceptable film thickness and solvent resistance but exhibits questionable salt spray performance, then the issue to address is the quality of the substrate and pretreatment. Are some of the parts excessively dirty (e.g., smut, forming oils, oxidation)? Is the pretreatment system adequate for the condition of the substrates? Is the pretreatment system adequately maintained? Are the chemicals within the supplier’s specified ranges? Are the rinses clean? Are the spray nozzles all in working order? Are the required solution temperatures being maintained within specification?

From what you’re telling me, I suspect that either the incoming parts vary widely in cleanliness and/or quality, or the pretreatment system is out of control. I suggest that you work closely with this customer to evaluate the quality of the incoming parts and the pretreat system, then rerun the same tests. It doesn’t hurt to include lab test panels as a benchmark alongside the line parts being evaluated.

Ask Joe Powder is a regular feature of Finishing Today magazine. Please send your questions to askjoepowder@yahoo.com.