WHEN SUCCESS IS ON THE LINE June 2014 SPRAY 35 Pitting corrosion causes blisters Figure 2 provides an example of pitting corrosion that causes coating blisters. The area under the blister could either fill with gas from the pitting corrosion or gas from corrosion and liquid that diffuses through the coating into the blister. Pitting corrosion as shown in Figure 2 typically leads to the leaking of liquid product or gaseous propellant. General corrosion causes blisters Figure 3 provides an example of blisters caused by general corrosion under the coating. The corrosion process draws liquid through the coating to the metal-coating interface and breaks the metal-coating bonds. The metal oxide produced by corrosion lifts the coating away from the metal to form the blister, as seen in Figure 3. Filliform corrosion Figure 4 provides an example of filliform corrosion. Filliform corrosion is similar to blistering caused by metal oxide corrosion product. Filliform corrosion is rare, and is usually found in the vapor areas of the container. The metal oxide produced by corrosion tunnels under the coating in the form of small meandering ribbons, as shown in Figure 4. Your questions/comments/suggestions for Corrosion Corner are always welcome. Please send them to rustdr@ pairodocspro.com. Please also visit our website, www. pairodoctspro.com, for more information. Thanks for reading Corrosion Corner and I’ll see you in July. Contact Spray Technology for previous aricles of Corrosion Corner. SPRAY Figure 3: Blistering caused by metal oxide corrosion product Figure 4: Filliform corrosion TIPPERS CAPPERS VALVE INSERTERS VALVE FEEDERS BALL DROPPERS (855) 841-3980 | www.haumiller.com/capper
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