May 2013, Vol. 240, No. 5


Letter To The Editor: Thermal Spraying For Corrosion Control

To The Editor:

I would like to elaborate on the March 2013 article “Hot-Dip Galvanizing Vs. Zinc Electroplating,” (pages 99-100). This article described “the two different process application and quality control aspects of zinc for corrosion control.” However, the article does not mention the use of thermal spraying (metalizing) as an application method for zinc coatings.

Zinc thermal spray coatings have been utilized since the early 1900s and offer excellent corrosion protection. Thermal spray coatings are designed to provide corrosion protection for more than 20 years. Thermal spraying zinc involves the projection of small molten zinc particles onto a prepared surface where they adhere and form a continuous coating. Upon contact, the particles flatten onto the substrate, freeze and mechanically bond.

Some important aspects one should consider when selecting a zinc coating process:

* In comparison to galvanizing, thermal spraying is a relatively cold process. The substrate temperature typically stays below 200F, effectively causing no risk of weld damage, distortion of the steel or thermal metallurgical degradation due to overheating.
* Coating application is typically achieved using an arc or frame spray gun; the average coating thickness is from 2-4 mils to over 20 mils with multiple spray gun passes. The operator does not require application expertise to achieve a uniform coating and can easily vary the thickness of the coating to suit the customer’s requirements.
* Thermal spraying equipment is inexpensive, portable and can be used in the shop or the field, allowing companies to perform in-house coating QA/QC.
* Thermal spraying is easy to apply to structures of any size or shape.
* It has been shown that thermal spraying zinc exhibits better corrosion resistance than hot dipped galvanizing for ductile iron piping.
* Thermal spray coatings show outstanding corrosion protection quality and are potentially the most durable and lasting zebra-mussel repellent coatings.
* Thermal spraying does not release volatile organic compounds (VOCs).

Nicole Karinchak, EIT
Zinc Technical Manager
Platt Brothers & Company
Waterbury, CT

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