Ask Joe Powder June 2024 – Cleaning problems and Galvalume

PPCJ’s regular columnist, Kevin Biller AKA Joe Powder, answers readers questions on all things powder coatings. Readers can submit questions to askjoepowder@yahoo.com

Hi Joe,

Can you recommend a type of vacuum to clean powder off the floor in our powder coating room?

Thanks,

Sandy Forsyth, Toronto

Hi Sandy,

Thanks for the question. It is important to choose the proper vacuum cleaning system to collect spilled or oversprayed powder coatings. Powder coating particle size ranges from slightly less than 1.0 micron up to around 100 microns.

It’s the smallest particles that can be troublesome for a vacuum system. Either they quickly clog the filters, or, if the filters are too coarse, the particles reenter the environment and defeat the purpose of cleaning. Indeed, you want to capture the finest particles and not redistribute them into your powder area, especially when changing colours or handling potentially incompatible powder chemistries.

You have a couple of choices when considering a vacuum system. You can simply tie into your existing dust collection system with flexible hoses, slide gates and appropriate nozzles. This is a low-cost alternative but limits your cleaning arena to the length of the hose and proximity to the powder to be captured.

Another alternative is to purchase a three-stage industrial-grade vacuum cleaner. The three stages enable the unit to pick up increasingly finer particles without clogging the filters. I recommend a HEPA-grade vacuum, which is capable of capturing particles as fine as 0.3 microns. This will cover the spectrum of powder coatings commonly used in industry.

Best Regards,
Joe

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Hey Joe,

We have a dedicated/automated powder line. The parts go through the wash stages and are powdered in an enclosed area. Powder guns are oriented from both the top and bottom.

We have a problem where powder collects on the top inside of the booth and eventually falls in clumps on the product. We have a regular cleaning schedule for the booth, but it is cumbersome and takes too much time.

Do you know of any way to prevent the powder from being collected in the first place or any other suggestions that would make this more efficient? I would appreciate any time you could spare to consider this.

Thanks,

Jeff Bockoven, Nebraska

Dear Jeff,

Sounds like a very aggravating problem. I recommend exploring a combination of design, process and materials to tackle the problem.

Design

I would consider replacing flat surfaces (if you have them) with curved ones. The curved surface will allow for better airflow and a potentially cleaner surface. Also check the air flow of your system near the top of your booth. Is there a dead space? Can your airflow be redirected to pull air from this area?

Process

Do you have adequate ground for your parts? Powder is electrostatically attracted to the closest and best ground. If your booth ceiling is conductive and well-grounded, then the powder will be preferentially attracted to this surface. Is your spray gun orientation and pattern too wide? Are you overshooting the top parts on your hangers and thereby spraying powder too high? Do your guns trigger too soon before seeing parts and stay on too long after the hanger has passed? Again, powder will look for a ground, which will most probably be your booth walls and ceiling.

Materials

Is the top of your booth comprised of metal or a lesser conductive plastic? Metal will attract powder much better than polypropylene or HDPE. A quick fix may involve installing an intermediate plastic baffle between your parts conveyor and the booth ceiling.

I hope that these ideas will help you in your quest to eliminate this problem. Please let me know how you progress.

Best Regards,
Joe

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Dear Joe,

I was wondering if you can powder coat over Galvalume with a clear coat.

Thanks in advance,

George Mazeika, New Jersey

Dear George,

Yes, you can powder-coat Galvalume with a clear coat. It’s very important to adequately clean and pretreat the Galvalume if you require any level of durability. Galvalume is nominally comprised of 55% aluminium, 43.5% zinc, and 1.5% silicon, which makes the surface more “aluminium-like” than “zinc-like.”

Because of this, you should be considering a cleaning/pretreatment technique that works well for aluminium rather than those used for steel or zinc. You should contact a reputable pretreatment chemical supplier. They offer comprehensive product lines designed specifically for non-ferrous substrates.

Identifying and implementing the appropriate cleaning/pretreatment system for Galvalume parts is only half the solution. The other half is maintaining the quality of these chemical solutions and operating your process within the proper control ranges.

I hope this helps. Please let me know if you have any other questions.

Best regards,

Joe