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Ask Joe Powder

"Ask Joe Powder"
"Ask Joe Powder" is a question and answer column authored by Kevin Biller of the Powder Coating Research Group. Mr. Biller has over 30 years experience formulating and manufacturing powder coatings. He welcomes your questions regarding powder coating technology. Please write to: askjoepowder@yahoo.com 

Kevin Biller
The Powder Coating Research Group
15 W. Cherry Street, 3rd Floor
Columbus, OH 43215
614-354-11988
www.powdercoatingresearch.com 



Dear Joe,
I do not know much about powder coating and was hoping you could answer a question for me. We have a Victorian kitchen sink that we are considering having powder coated. We will be washing dishes and using the sink for food preparation (washing vegetables and other food items in the sink, etc.). I read on your site that if a container is to be used to store food items, powder coating used should be food-safe. What about for a kitchen sink? We have young children and want to make sure things we use are safe for them. Are there advantages of using powder coating over other finishes such as acrylic (the sink is porcelain enamel, but we have not been able to find anyone that does this type of finish anymore)?

Thank you in advance for any assistance you could provide.

Julie

Dear Julie,

Thanks for your question and I appreciate your concern. You are wise to carefully consider which finish to use on your kitchen sink. I can think of a lot of reasons - contact with your children, contact with food (cleaning, soaking,etc), contact with future inhabitants of your home (how about giving the newborn a bath in the sink?) and even the notion of introducing compounds into our water system. Luckily there are answers to your concerns. As a matter of fact, food-grade powder coatings are routinely applied to the wire shelving used in refrigerators.

So here is what I suggest you do, request that your powder coater use an FDA acceptable powder coating to refinish your sink. The majority of these come in any color you like as long as it's white. If you want a custom color you may have a bit of an effort to get one made. If necessary I can chase someone down who may be able to make one for you. It is also important to adequately prepare the old finish to ensure good adhesion of the powder coating. This entails roughening the surface (media blasting is a good idea) and then thoroughly cleaning it before the powder coating is applied.

As for a competitive finish, I'm not sure what is still available. However if you choose powder coating, you will be kind to the environment (no solvent or paint sludge) in addition to getting an excellent finish.

Joe

Joe we have been painting these parts for another company. Lately we have had trouble with out-gassing. I think the quality of the aluminium has decreased. We are using a Midnight Black Wrinkle. Our pretreatment chemicals use a 5 stage wash. I really think it is the aluminium since the steel parts painted at the same time are perfect. What are your thoughts?
Jeff

Dear Jeff,
Indeed it sounds like your aluminium may be declining in quality. Before you conclude this, you should also take a close look at your own process. Has the pretreatment system changed? Is it in control (pH, solids, temperatures, etc.)? Are you running your production line at the same speed as before? Are you running the same amount of parts through the finishing system? Is your oven steady and in control?

Outgassing is most common with cast alloys (aluminium and magnesium) and galvanized substrates. A high level of porosity can spell trouble. If you suspect the aluminium is getting worse I suggest you take a few parts and preheat them, allow them to cool to just above ambient temperature then powder coat them. The preheating should expel any entrained volatiles and the finished part should not exhibit any blisters from outgassing. If this is the case you should get in touch with your part supplier to investigate a change in the quality of their parts.
Alternately you can also investigate the use of an “outgassing forgiving” powder coating. Many powder suppliers offer these. These minimize the effect of inconsistent porosity in substrates.

I hope this helps.

Joe,

I found your website and thought maybe you could help me. I just paid a lot (way more than I planned) to have a polyester powder coated metallic tin ceiling installed. The problem is it turned out a lot darker than I had envisioned and I think I need to paint over it. I'm nervous to do anything that would damage it or cause it to look worse. How do you suggest painting it? I would like to have some of the bronze come through. It is only an 8 foot ceiling so I don't want to see any brush strokes.
Any help or suggestion would be greatly appreciated.


Hi Lisa,

This sounds like a delicate project. Sorry to hear you're unhappy with your powder coated ceiling. I have a few questions. Was this a remodeling project where the pieces were removed from the ceiling then coated? Or were they ceiling panels that were powder coated by the manufacturer? Are the ceiling pieces now installed? Is the powder coating a clearcoat or an opaque material? Fill me in on these details and I will do my best to help you.

We had a popcorn ceiling and wanted a tin one. The remodelers installed plywood and then put in the tin ceiling that I ordered from American Tin Ceilings. The 60cm x 60cm pieces are mocha bronze which were powder coated from the factory. The ceiling is up and it made our kitchen a lot darker than I thought it would be and my husband hates it. We are thinking about painting it which is killing me since I could have paid a lot less to get white tin vs. what I bought.

Thank you for emailing me. I wasn't sure you would.


Hello Lisa,

Hmmm, I can see your problem. Sometimes a 60 x 60 panel looks a lot different in your hands than a bunch of them covering your ceiling. I looked at American Tin Ceiling's website - they have beautiful stuff. I could see putting one of their products on my dining room ceiling.

The project is salvageable. Here is what I would do. Choose a high quality oil-based flat white paint to coat the ceiling. Rustoleum has a product that should work (7790 1G Flat White Rustoleum). If you are concerned with brush marks, you can spray the paint on the ceiling with an airless spray unit. Airless spray units are not difficult to operate and can be rented at your local DIY. Ensure that the ceiling is clean (no dirt, oil or fingerprints). Wiping it first with acetone or denatured alcohol is a good idea. I would spray a loose piece before hitting the ceiling.

Life has its little bumps in the road. With a little patience and perseverance you should be able to transform your new ceiling into a unique and beautiful feature of your kitchen.

Good luck and please let me know if I can be of any further assistance.