Keep away oxidation

Russ Kratowicz, P.E., CMRP, executive editor, searches out what the Web tells us about rust and corrosion control.

By Russ Kratowicz, P.E., CMRP, executive editor

Element No. 8, oxygen, is essential to almost all life on this planet, but its high reactivity endows it with a dark side. It easily combines with most metals to produce an oxide, which is generally undesirable in the industrial arena. There are some exceptions, the most common being lead and aluminum. The oxide that forms on these metals is relatively transparent and dense enough to protect the substrate from further attack by oxygen molecules.

In general, water, so common in nature, accelerates oxygen attack – corrosion – on susceptible metals. The best that a plant professional can do is stem the tide, but it requires continuous diligence to protect the capital assets that provide your livelihood. Years of empirical testing and applied theory have led to several technologies that minimize corrosion. Many of them are highlighted in the digital morass we call the Web. So, join me in search of practical, zero-cost, noncommercial, registration-free resources that will keep your plant looking like a shiny, new nickel. Remember, we search the Web so you don't have to.

Getting off the ground

We’re accustomed to believing, sometimes incorrectly, that nasty industrial air pollutants cause excessive corrosion on any metallic item placed outdoors. According to the first Web site citation, the corrosion rates in cities we associate with heavy industry aren’t nearly as bad as the rates at venues we’d consider a bit more Edenic. For example, the rate in Pittsburgh is 1.2 mils/year, Cleveland suffers with 1.5 mils/year and East Chicago rots at 3.3 mils/year. Contrast those numbers with the 42 mils/year you’ll experience at the Kennedy Space Center. With the reliability of the shuttle and its ground support hardware being so critical to a safe launch, one wonders why NASA set up shop there. The good news is that NASA’s Corrosion Technology Laboratory knows how to prevent the metallic degradation that can drop into your back yard the stuff intended for orbit. And, NASA will reveal some of what it knows if you launch your weightless mouse around http://corrosion.ksc.nasa.gov. The “Corrosion Fundamentals” tab offers a brief overview of the electrochemistry involved, the multiple types of corrosion, corrosion control and a list of additional sources of information. The latter option has a link to NASA-KSC TM-584C, "Corrosion Control and Treatment Manual," a 36-page document that discusses applicable MIL specs and suitable products. The “Resources” tab gives access to publications, the scholarly works written by engineers at the lab.

Dollars and rust

Not only is corrosion a pain in the patootie, but it comes with a cost that degrades your industrial financial performance and, if addressed improperly, enhances governmental budget shortfalls. Corrosion proceeds in only one direction, and it takes cash to hold back that real-world example of rising entropy. The quantity of cash needed involves some staggeringly large numbers. At least one company, CC Technologies, Dublin, Ohio, tracks the financial effect of corrosion on its Web site, www.corrosioncost.com/home.html. It reports that production and manufacturing face more than $17 billion in corrosion costs, and that only accounts for nine select industrial categories. Visit the Web site if you want details about the cost of corrosion on utilities, transportation, infrastructure and government, plus, of course, the nine industrial elements. The tab tagged as “Corrosion Control Methods” will show you the methodology used to develop the cost data, but not actions you can take to control rusting.

Hot rot

A plant subsystem that might fall victim to the ravages of unnecessary corrosion is the boiler and the various pieces of hardware in the steam system. By definition, boiler corrosion starts with elevated temperatures. After that, it doesn’t take much in the way of incorrect pH, dissolved or suspended solids, oxygen, high velocity and impingement to set the scene for corrosion-induced reliability problems. You might be able to get a little more performance out of your boiler if you read the material that GE Water & Process Technologies, Trevose, Pa., posts on the Web. The company provides the full text of a 40-chapter book that explains the mysteries of water treatment, boiler systems, cooling water systems, chemical feeders, wastewater and gas cleaning systems, and water analyses. This isn’t light reading – the explanations are fairly technical. Go to www.gewater.com and enter the phrase “handbook of industrial water treatment” in the search box. Somewhere in the results will be an entry showing the handbook name, but without any reference to a particular chapter or topic. That’s the link you want. If it doesn’t load properly when you click on it, try again with a right-click to open the link in a new window. Four of the chapters about boilers are explicitly about corrosion, whereas one chapter in the cooling water section mentions it. Other chapters might have additional information about the topic.

E-book

In the good old days, researching a technical topic meant a trip to the reference section of a library if you lived in a larger town, or a lot of searching with phone calls and catalogs if you didn’t. That approach is snail-like compared to the Web, which allows us to dig deeply in as many places as necessary in search of the information that resolves the question. The most useful Web sites for this purpose provide full-text access to books that address corrosion. We found a winner this month in the Web site associated with an initiative called the Whole Building Design Guide, which covers so much territory that you should explore it on your own when you get bored sitting at a desk.

In the interim, if you’re partial to using industrial coatings to prevent corrosion, you can access the online, 250-page “Unified Facilities Criteria - Protective Coatings and Paints” merely by visiting http://artikel-software.com and entering the phrase “protective coatings” in the search box. You’ll learn about coating compositions and curing mechanisms; environmental, occupational and safety issues; coating selection; coatings for specific uses; surface preparation; application; writing painting contract specifications; painting inspection; inspection instruments; paint failure analysis; maintenance painting and safety practices. Use this site when you want to complete a project that’s in accord with various military specifications.

But, if your interest lies with cathodic protection to prevent corrosion, then enter the phrase “cathodic protection” in the search box. This will return “Cathodic Protection for On Grade Storage Tanks and Buried Piping” by John Fitzgerald. The content, in the form of a slide show given at a conference, is a bit light on text, but it should give you some valuable insights for future research.

Hidden hazards

Insulation abounds in a typical plant setting. It serves two primary purposes. First, it prevents contact with temperature extremes that could otherwise wreak havoc on body parts and sensitive hardware. Second, it helps minimize your plant’s carbon footprint. Insulating corrosion-susceptible surfaces, however, introduces a gamble into the certainty you seek for your reliability initiatives. Corrosion can form under the insulation. This invisible threat represents a safety risk if it compromises a system’s pressure capability through reduced vessel and pipe wall thickness. But, insulation, once installed, is rarely removed routinely. One solution to this dilemma comes from the American Society for Nondestructive Testing Inc. in Columbus, Ohio. The organization’s Web site offers a short article titled “Inspection Techniques for Detecting Corrosion Under Insulation.” It explains, in simple terms, when such corrosion occurs, the locations you should expect to see it and possible nondestructive ways to seek it out. Push your mouse to www.asnt.org, where, on the left side of the screen, it is to activate the drop-down menu behind “Publications” and click on “Materials Evaluation.” Then, click on the “Back to Basics Archive” link (underlined in blue) and scroll down to the February 1997 article.

Because insulation is a key element in this matter, you might want to learn what the National Insulation Assn., Alexandria, Va., has to say about corrosion under insulation (CUI). Pay a visit to www.insulation.org/articles, where you should perform two searches. For the first, enter the phrase “toolbox for prevention” in the title/intro keyword slot of the quick-search feature. This gets you a copy of “Toolbox For Prevention of Corrosion Under Insulation” by Gordon H. Hart, which appeared in the March 2008 issue of Insulation Outlook. It’s a 2,900-word article that addresses protective jacketing, insulation maintenance, pipe coatings and insulation properties, each a variable that affects CUI. Then, repeat the search using “prevention measures” in the same search box to get your hands on “Corrosion under Insulation: Prevention Measures” by Hira S. Ahluwalia. This 1,900-word article will tell you about four innovative approaches that petrochemical plants are using to combat the problem.

Buried pipe

According to the Ductile Iron Pipe Research Association (DIPRA), Birmingham, Ala., there is much to recommend using ductile iron and cast iron products when you need to lay underground lines for a variety of services. Strength, cross section area for flow, life cycle cost and corrosion resistance are some of the factors the organization cites. That last claim was enough justification to dig into the evidence DIPRA puts forward to support its assertion. And you can see the results of my bit of low-cost research by casting a click at www.dipra.orgto click on “Publications” at the bottom of the page and then “Corrosion” when the page loads. The last three entries seem most relevant. They explain how and why a loose polyethylene wrap prevents soil-induced corrosion, explores the effect that overhead AC power lines have on buried pipe when both services share the right-of-way, and discusses the effect of stray currents on the pipe. The last aspect is important if you’re using cathodic protection for other lines in your plant.

From the consultant

If you can’t accept the word of a freelance corrosion consultant, who will you believe? Corrosion Doctors is the name of a Web site operated by Pierre R. Roberge, Ph.D., P.Eng., a professor at the Royal Military College of Canada, Kingston, Ontario. He’s got the credentials and his site has an intense, single focus on all things corrosion, working upward from the periodic table through biographies and inventions of the heavy hitters in the field and onward to eliminating the pesky phenomenon. And, he claims he’s done it using only about 1,600 pages and thousands of external links. There’s much theoretical and applied material to explore at http://corrosion-doctors.org. For example, you might want to start with a click on the phrase “prevent and control” in the paragraph at the middle of the screen. That’s where Roberge provides access to a dozen of what he calls information modules, each of which addresses a separate aspect of this corrosive discipline. This link-rich environment explores corrosion basics, cathodic protection, inhibitors, monitoring, test methods, inspection, electroplating, coatings and more.

Without comment
www.corrosion.com/publication.html
www.projectsmonitor.com/detailnews.asp?newsid=7487
www.cee.vt.edu/ewr/environmental/teach/wtprimer/corrosion/corrosion.html

E-mail Executive Editor Russ Kratowicz, P.E., CMRP, at russk@putman.net.

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