Water Well Journal

August 2015

Water Well Journal

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W hat you can't see can't hurt you, right? False. When it comes to cor- rosion, what you can't see could cause costly problems for you down the road. "The rusting process is like a slow fire," says Chad Grignon of Pine State Drilling Inc. in Athens, Maine. "If you can get to it early and neutralize it, a piece of equipment can last a long, long time." The key is to catch it early. If not, it can eat away at your equipment—and your profits, too. Often referred to as rust, corrosion occurs when metals are exposed to ele- ments in our environment, including moisture and chemicals. The metal de- grades over time, which causes physi- cal, mechanical, or aesthetic damage. Last month, we covered two com- mon forms of corrosion. Pitting corro- sion is a localized form of corrosion that forms small cavities or pits. Uniform corrosion, the most common form, is an easy-to-predict form of corrosion causing uniform loss of metal across an entire surface. This month, we'll cover the last two common forms of corrosion: crevice and galvanic corrosion. Crevice corrosion Crevice corrosion can be the toughest to find early because it's often hidden from view. It's also harder to prevent because it can be difficult to keep small crevices free of damaging chemicals like road salts. Much like pitting corrosion, crevice corrosion is a localized form of corro- sion that occurs when chloride-bearing solutions are left stagnant in crevices. It's most likely to occur in seawater ap- plications, but chloride de-icers used in states plagued with snow and ice during the winter months also cause problems. Crevice corrosion is common in wheel wells, bumper skirts, and fenders where sand and rocks coated with road salts become trapped. "It starts rusting from the inside out," says Ryan Budke, general manager of Shawver Well Co. Inc. in Fredericks- burg, Iowa. "It's a trapped place and it starts a hole right there." Galvanic corrosion Galvanic corrosion occurs when two dissimilar metals are electrically con- nected in a corrosive environment. When this happens, the less noble of the two metals will begin to corrode. Although not a common problem on equipment, galvanic corrosion may occur in water systems where two different metals are used. "(Homeowners) will have copper pipe, and somebody puts a galvanized pipe in between two copper fittings," says Sam Tyler, CPI, owner of Tyler Well & Pump in Carver, Massachusetts. "We see corrosion happen a lot when that takes place." How manufacturers prevent corrosion Because corrosion is so widespread, manufacturers are doing whatever they can to make sure their equipment has longevity in the field. To discourage corrosion from begin- ning in the first place, many equipment manufacturers are using corrosive- resistant materials and paints in the construction of their equipment. GEFCO, for example, prevents gal- vanic corrosion by using all steel in the construction of its rigs. Not only is it able to better withstand the weight of the equipment, but the rigs are less likely to experience galvanic corrosion. "We used to use some aluminum in our construction, but we've gone back to all steel," says Chip Nelson, Midwest sales manager with GEFCO Inc. in Enid, Oklahoma. "We had a few issues with the two metals next to each other, and it's better for painting and sealing when we're using the same product throughout the whole process." Each piece of metal is sandblasted, prepped, and painted before putting it on the rig. This helps reduce the likeli- hood of all types of corrosion, whether that's crevice and galvanic or pitting and uniform. To address issues with crevice corro- sion, rig manufacturers like GEFCO seal up seams to reduce the number of crevices where corrosive agents can get trapped. When two pieces of steel are put to- gether that aren't load bearing, the entire seam doesn't need to be welded. But, manufacturers like GEFCO are taking the extra step by sealing the entire seam. "If there's an area that's not continu- ous welding, we'll take a seam sealer and seal that area off," says Greg Haub, who works in manufacturing at GEFCO. "This way, moisture can't get in behind the layers of material." Out of all forms of corrosion, gal- vanic corrosion is one of the most pre- ventable. Because galvanic corrosion occurs when dissimilar metals are bolted, welded, clamped, or resting against one another, you can prevent it by not using these metals next to each other. Many equipment manufacturers already avoid putting dissimilar metals together. If there are dissimilar metals next to each other on a piece of equip- ment, you can discourage corrosion by preventing electrical contact between the two. Do this by using non-conductive ma- terial such as rubber or plastic between the two metals. Teflon coatings can also prevent the two dissimilar metals from corroding. Galvanic corrosion is more likely to be present in water systems where steel Part 2: How to prevent crevice and galvanic corrosion before it starts By Jennifer Strawn CORROSION continues on page 30 Corrosion occurs when metals are exposed to elements in our environ- ment, including moisture and chemicals. " It ruins a good truck within a matter of years." WWJ August 2015 29 Twitter @WaterWellJournl

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