Corrosion is an inevitable concern in plants throughout industry. Reaction with the environment causes this naturally occurring, gradual deterioration of a substance or its properties. The phenomenon is costly in terms of machine or infrastructure failure and repair, contaminated product, human safety, environmental damage and downtime resulting in lost production. Corrosion reduces the useful life of equipment and increases the risk of litigation. Corrosion Doctors, a Web site dedicated to the topic, reports that corrosion is the largest single cause of plant and equipment breakdown in the process industries.
Others agree. Corrosion costs the United States more than $276 billion annually, of which more than 30% could be prevented through the use of optimum corrosion-management practices, according to the National Association of Corrosion Engineers (NACE) International. Indeed, proper monitoring and control of corrosive environments and corrosion-induced damage is essential to mitigate operating risk and optimize process operations.
Corrosion management: An effective corrosion-management program begins at plant and equipment design by selecting corrosion-resistant materials appropriate for the application. In production, perform regular inspections and maintenance on corrosion-prone equipment, as well as any monitoring systems or inhibitors installed. Corrosion-monitoring and measurement tools facilitate inspections and maintenance.
Monitor and measure: Ready access to information regarding corrosive conditions and deterioration rates allows companies to make better decisions about the method, urgency and cost of remediation. Corrosion monitoring provides early warning of damage and pinpoints the problem locations. Monitoring also helps to determine the effectiveness of repairs, treatment or prevention programs. Finally, it helps to connect corrosion trends with process variables.
Monitoring systems: A variety of direct and indirect, intrusive and nonintrusive, online and offline measurement techniques are available. Probes inserted in the process stream can sense and signal corrosive activity or measure metal loss. Smart pigs can be pushed through a pipeline to detect corrosion and dents. Laboratory analysis of process gas samples can detect impurities and other chemicals that promote or signal corrosion. Coupon exposures, data loggers, surveillance sensors and cathodic protection surveys can be employed for monitoring purposes.
Corrosion-measurement tools and techniques are becoming more sophisticated, allowing a more proactive response. Real-time, online measurement tools expedite awareness of any deterioration so that corrective action can be better planned. These highly sensitive systems, implemented within a plant or in the field, generate and relay signals immediately as the corrosion rate changes.
Technology facilitates electrochemical measurement of corrosion and scaling for industrial applications. An example is InterCorr International’s SmartCET technology, which monitors localized and general corrosion online and in real-time. The company’s PS Biofilm line of portable monitoring units allows online and sidestream corrosion assessment capabilities that can be used in lab, plant or field environments.
Using the information: Data derived from corrosion monitoring can be used to select longer-life materials and develop more effective repair strategies. Internal or external coatings or liners can be applied to prevent or repair damage. Corrosion can also be inhibited with cathodic or anodic protection systems and by dosing process streams with additives.
The selection of corrosion-resistant materials, chemical inhibitors and remediation techniques depends on the specific function and location of the equipment. Process fluids and chemicals promote internal corrosion, and external atmospheric conditions promote external corrosion. There’s not one single technique that detects or mitigates all the various conditions. To help isolate the right materials, try MatWeb’s searchable database of the chemical, physical, and mechanical properties of most engineering materials. Companies such as CorrTech Inc. provide infrastructure assessment and rehabilitation services.
More information: Attend NACE International’s Corrosion/2005 conference April 3-7, 2005, in Houston. The show will include exhibits and technical presentations that showcase the latest advancements in corrosion-control research and products from around the world.
Visit the Corrosion Doctors Web site. This educational portal explains corrosion from the ground up, including how to quantify corrosion damage and the benefits of proposed solutions.
The American Society of Testing and Materials (ASTM) International is another helpful resource. The organization’s Corrosion of Metals technical committee is instrumental in developing and promoting standards relating to corrosion and methods for corrosion-protection.
E-mail Contributing Editor Sheila Kennedy, managing director of Additive Communications, at Sheila@addcomm.com.