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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: firstname.lastname@example.org
The Powder Coating Research Group
15 W. Cherry Street, 3rd Floor
Columbus, OH 43215
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.
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 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?
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.
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.
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.
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.