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"Best Protection for Parking Meter"



 

Q. Hi,

We design and manufacture Electronic Multi bay parking meters sold world wide with the USA seeing the major overseas sales Berkeley, Houston, San Francisco.

The question relates to the protection of a new product that is made of mild steel of fabricated construction. I am looking at either Galvanized finish only or Galvanized and Polyester powder coated or Zinc plated and Polyester powder coated. Other? The conditions of service are "on the street" from snow and ice and salt to hot and steamy at the beach. The installation is to concrete footings and there could be some water pooling around the base. Constraints are cost! What is the best protection for the bucks? I know little of Galvanizing other than the basics and the finish that the marketing department will accept is the galvanizing which exhibits the crystal structure on the surface - Is this achieved with processing or does this develop over time?

Chris Gollin
- Sydney, NSW, Australia
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A. A powder coating or other organic coating will protect only if the component is not scratched, which is probably a bad bet for a parking meter. Either zinc plating or galvanizing will provide the sacrificial zinc layer that protects despite scratching. Galvanizing is usually much thicker than plating and is acceptable for outdoor exposure without painting whereas zinc plating alone would not be enough. If the galvanized appearance is satisfactory, that should do it, but I think the powder coated finish on top of plating would look much nicer.

Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
^


 

A. I agree with how Mr. Mooney answered your question. That is the galvanizing of these parking meters is most likely your best option. In addition to this I also agree that you would be pleased with the enhanced aesthetics Powder Coating has to offer.

With this being said I would like to make you aware of the issues involved with Powder Coating over galvanizing. Because of the inherent properties of galvanizing the surface must be prepared differently for powder coating than a typical substrate. You can gain more knowledge of this through the "American Galvanizers Association". I am not affiliated with them, however, I used to operate a powder coating job shop before opening my own business as a equipment dealer/consultant & have been faced with this same dilemma. I found most of my answers through these people. Their website is www.galvanizeit.com.

Eric Beeson
- Hastings, Nebraska, U.S.A.
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Q. Can powder coating be made a better corrosion resistant finish than galvanizing for outdoor street light poles? Can life of powder coat be higher than hot dip galvanized pole? What is salt spray test life of PU based powder coat vs galvanized part.

Regards,

Vinod Mehta
powder coating - Faridabad, Haryana, India
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November 2013

A. Hi Vinod. Great question that raises a couple of different issues...

First, completely forget salt spray hours please; it will seriously harm your decision process. Salt spray testing is a quality assurance test. If you have a good process, and it usually survives xxx hours of salt spray, something has gone bad if the salt spray hours dive.

But never try to use salt spray hours as part of the design or coating selection process! For example, galvanizing can last 75 to 100 years with no maintenance under reasonable outdoor conditions. There is no other finish that comes anywhere close to an equal life. But salt spray life is not good because the durability of the finish relies on the slow formation of a glassy and extremely durable zinc carbonate surface as the zinc reacts with carbon dioxide in the air ... and this is absent in salt spray testing.

Paints and powder coatings will outperform galvanizing in salt spray testing, but offer no sacrificial protection. With proper phosphatization pretreatment, good powder coatings may be fine, and in very wet situations might equal galvanizing. Obviously, the best finish is galvanizing followed by powder coating, but this can be cost prohibitive. Good luck.

Regards,

Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
^

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