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Ted Mooney, P.E. RET
Pine Beach, NJ
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for Metal Finishing since 1989
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Powder coating selection for bathroom accessories
Q. Hi,
My name is Shourya Asthana, and I am an industrial designer working for a US based importer.
Currently I am working on a project of Bathroom accessories, which need to be made in mild steel.
But as the environment inside the bathroom is very damp and full of moisture, I want the mild steel substrate to be powder coated.
Please advise, what kind of powder coating will give full protection from corrosion, as we give 6 years of guarantee on the products that we manufacture.
Industrial Designer - New Delhi, INDIA
2005
A. Dear Asthana,
As per my experience polyester based powder coating gives highest protection in damp condition.
Do zinc rich phosphate treatment before applying powder coating for better corrosion resistance.
- New Delhi, India
2005
Type of powder coating for a home bathroom environment?
September 12, 2016Q. Hello,
I am preparing manufacturing and coating specs for a series of metal accessories for the bathroom, such as a towel rack. I was wondering what would be the best type of powder coating to ensure long-term resistance to abrasion, fading from UV, and corrosion.
Bathrooms are of course very humid environments, the edges of accessories seem vulnerable to abrasion, and and there is always the risk of people bumping hard objects into them.
We also have some smaller counter-top accessories which could potentially fall on the floor.
I am thinking we probably need to go with AAMA 2605 level fluoropolymer.
I was also considering having the counter-top objects made out of 304 stainless, to prevent rust in the event the powder coat does become damaged through a fall.
What do you think? Are these approaches overkill? I have yet to drill down costs...
Thanks in advance for your feedback.
Patrick
Product designer - Montreal, Qc., Canada
A. Hi Patrick. Yes, AAMA 2605 fluoropolymers may be overkill as yours is an interior application with no exposure to strong sunlight, or the high temperatures of summer sunshine or the cold temperatures of winter outdoors, etc., which the fluoropolymers are designed for. Polyester is probably fine, but you should have a good zinc phosphate pretreatment, and you should also consider electrocoating after the phosphate and before the powder coating if there are any seams or if there are deep recesses where Faraday cage effects may interfere with good powder coating. Good luck.
Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
September 2016
A. In my opinion, powdercoated steel is not well protected from corrosion in a humid or wet environment, and you need more than a single coat of polyester.
Stainless in 304 grade seems expensive
I wonder if a two coat system of say epoxy, then polyester topcoat would be better?
Powdercoating, the same as paint, is porous.
Geoff Crowley
Crithwood Ltd.
Westfield, Scotland, UK
September 13, 2016
A. Why do you want to use powder-coated steel for bathroom fixtures? The norms in the industry are aluminum, brass, and stainless steel because of the potential corrosion problem. If you make the parts out of aluminum you can anodize them. For brass, you can go with a patina (acid etched finish that changes with time), powder coating, plating, or PVD/plating. If stainless is the choice, then PVD would be the best finish.
Jim Treglio - scwineryreview.com
PVD Consultant & Wine Lover - San Diego,
California
September 14, 2016
Thanks for your answers so far. We are interested in powder coating for the color possibilities.
Working with stainless steel is about 20% more expensive, but then requires some surface preparation for proper powder coat adhesion as I understand it. Stainless steel may be mandatory for hotels, for example.
I've seen powder coated cold-rolled steel edges rust in a bathroom environment, and I've seen powder-coating chip off of a stainless steel object that fell on the floor. So I'm hoping to avoid these problems.
- Montreal, Canada
September 28, 2016
Q. For greater protection, what about powder coating over a metal varnish? I have heard of some companies doing this.
Patrick Pierce [returning]- Montreal, Canada
September 29, 2016
A. Hi Patrick. I'm not sure what this "metal varnish" is that you're speaking of. I think the best overall solution would probably be to use stainless steel, properly phosphatize it, and then apply cathodic electro-deposition paint (CED / Electrocoat / Electrophoretic Lacquer). That would offer you virtually any color available in powder coating.
Our very knowledgable contributor, T.S.N. Sankara Narayanan, says in topic 73 that cathodic electrochemical treatment can phosphatize stainless steel. You might also try simply blasting the stainless and applying the CED coating on that. Various mandrel bend tests and impact tests on samples could determine if the adhesion level is sufficient to sustain dropping on a tile floor without chipping.
Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
September 2016
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