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Corrosion Protection

on October 16, 2013

As part of Wheatland’s initiative to educate our customers on our products and processes, we have developed this Q&A resource to help you to understand what corrosion protection is, the industry requirements and how Wheatland meets those requirements, and which those environments require special coatings for protection. We have enlisted our in-house expert, Mike Ziegler, product development, coatings and quality, to answer a few questions about this subject.

Corrosion 2Q: In the steel pipe world, what does corrosion protection mean?

     A: Basically, the idea of corrosion protection in our industry comes down to keeping the steel of the pipes from being converted to iron oxide (rust). The main way in which this is done is to coat the pipe with something that prevents that oxidation reaction from occurring. The two most common examples of this are galvanizing and painting.

Q: What are the industry requirements for corrosion protection?

     A: Given the wide variety of end-markets that we support, that’s a complicated question to answer.  For pipe products that go into electrical applications (e.g., conduit), there are a number of requirements maintained by organizations such as Underwriters Laboratories (UL). These requirements detail the length of time that a pipe must be able to withstand being exposed to various corrosive environments without degradation. Other end-use areas — such as sprinkler pipe, gas transmission pipe, drill casings, drinking water piping and others — are also governed by various regulations that address the type of environments those pipes are likely to be exposed to as well as how long the pipe should be able to withstand those environments. For example, the industry requirement for corrosion resistance in electrical conduit is 600 hours of exposure to a saltwater mist without any visible red rust formation on the surface.

Q: How does Wheatland meet these requirements?

     A: The simple answer is through the use of protective coatings. Depending on the end-use, that protective coating could be a rust-preventing oil, varnish or acrylic paint applied to the pipe. It could also be a complete conversion of the surface of the pipe through a process such as galvanizing, which creates a layer of zinc alloy on the surface of the pipe. For many of the applications of our pipe, we will use a combination of several different coatings to get the ideal balance of properties.

     A great example of this is two of our A513 galvanized mechanical tube products. Both our SURcoat and ThunderCoat™ products are protected with a layer of zinc, making the coated tube resistant to steel oxidation (red rust), as well as a layer of inorganic coating and a layer of organic coating to resist to oxidation of the zinc layer (white rust). The thicknesses of the coatings are different in the two cases because SURcoat is meant for indoor applications and those in which surface smoothness is critical; ThunderCoat is meant for applications in which standalone resistance to the outdoor elements is the most important attribute.

Q: What are typical environments that require special / additional coatings for corrosion protection? 

     A: Any time steel (or, more specifically, the iron in steel) is exposed to water, oxidation of the iron can occur — and this results in corrosion. The presence of salts, acids or bases really accelerates that reaction, so the most challenging environments to avoid corrosion are those with both water and one of these catalysts. One obvious example would be marine or coastal environments. These environments have plenty of water and plenty of salt, so they really require very robust, high-performance coatings systems. One challenging environment that I find particularly fascinating is the inside of sprinkler pipes. That’s obviously an environment where the pipe is exposed to water, but what many people may not know is that a poorly maintained sprinkler system can become a breeding ground for bacteria — and these bacteria can generate acidic waste products that corrode the pipes. This is the reason we apply our MIC SHIELD™ coating on our sprinkler pipe products. This antimicrobial coating helps protect the inside of our pipes from these types of bacteria.

corrosionHave there been advancements in this area over the past decade to improve corrosion protection performance? Absolutely! According to a recent study, the worldwide cost of corrosion damage is currently estimated to be $2.2 trillion dollars —roughly 3 percent of the world’s GDP. With a problem that big, there is a lot of interest in improving the quality of the solutions that are available. Coatings companies are constantly improving the effectiveness and longevity of the paints that they supply. We’re continuously improving our galvanizing operations and looking for more effective alloys to use in our processes. One specific area that has received a significant amount of attention over the past few years is that of nanotechnology. The maturity of this field has led to the development of a range of new materials with extremely interesting properties. We’ve been aggressively exploring this area and have found some very promising initial results using nanoparticles to greatly increase the hydrophobicity (water repellency) of the surface of products, which we hope will eventually lead to a new generation of corrosion-resistant coatings.