Asset preservation is a key long-term strategy for all water and wastewater systems. Many of the technologies employed in developed countries can be transferred to emerging countries as they expand their water and wastewater infrastructure. Corrosion avoidance through proper selection of engineering materials, proper coating systems, and use of corrosion mitigation technologies should result in preservation of these assets.

 Water Distribution 

Establishing a healthy environment and guaranteeing sound nutrition in every country is a huge, so far unsolved, problem. The most important component to this is water: its abundant availability and its healthy distribution. Water is a basic and key factor in nutrition. Therefore, distribution of water with defined purity is an essential contribution to health and nutrition worldwide.

Water distribution requires a combination of piping, tanks, pumps, fittings, and plumbing systems. Selected materials for construction can greatly impact water quality and properties. For example—as stated in NACE technical paper C2013-0002817— the European Drinking Water Directive, in combination with the European Standard EN 12502, provides guidelines that describe the boundary conditions for safe and healthy water distribution. This standard relates to the concentrations of metal ions in the water, which limit the concentrations for specific ions and particulate compounds of elements including lead, copper, iron, nickel, zinc, cadmium, and aluminum. The metal ion concentration in the drinking water depends on the material selected, such as steel, galvanized steel, copper, brass, bronze, stainless steel, and plastic materials, and on the water quality with dissolved solids and microorganisms.

Thus, the pH of the water determines not only the likelihood of corrosion failures (e.g., by pitting) but also the corrosion-related content of metal compounds. Based on these considerations, a conclusion may be that it is best to use plastic materials for water distribution and storage. However, plastic materials are not immune to degradation, and they may facilitate biofilm formation, causing other problems pertaining to hygiene and other types of corrosion.

While corrosion can be internal from water being transported through a distribution system, materials of construction can also be impacted by external corrosion from aggressive atmospheres, soils, and groundwater.

Contributors at various World Corrosion Organization (WCO) workshops have emphasized that assets are ruined by materials deterioration because of nonexistent or inappropriate corrosion management plans, inadequate maintenance, improper inspection, lack of know-how, lack of discipline, lack of consistencies, and—the greatest problem—lack of corrosion awareness within the companies, including at the management and decision-making levels.

Awareness and competence in corrosion control must be supported and improved worldwide. Asset saving needs implementation of corrosion audits, corrosion assessment, and corrosion management. Promising examples of successful knowledge transfer from advanced countries to less advanced countries in corrosion include risk-based inspection, life-cycle analysis, appropriate corrosion control measures, and corrosion management.

Controlling Corrosion 

The safe distribution and storage of water is paramount to ensuring sound nutrition and asset preservation. From the standpoint of internal corrosion, best practices have been established in developed countries that allow the distribution of high-quality water with a low likelihood of corrosion failures. However, although implemented in underdeveloped countries, these practices are limited in actual practice. Simple systems for communities may include a basic drilled water well and hand pump to extract the water. Water quality can vary significantly, and in-place materials can introduce harmful levels of detrimental elements (i.e., copper and lead) or reveal high levels of internal corrosion. Selection of materials with low corrosion rates is still needed to reduce the metal ion release rate for a given class of metals.

Source waters, either ground or surface, require some level of treatment prior to introduction to the distribution system to avoid health issues. Additionally, appropriate water conditioning can determine the likelihood of distribution material corrosion failures. Water installation systems and plumbing techniques need to be improved in underdeveloped countries to reduce this issue. Again, although plastic materials show promise, they need to be carefully selected to assure sustainability.

Failures of water distribution mains due to external corrosion are further examples of corrosion-related failure from an aging infrastructure that are frequently encountered. A survey carried out in Europe in 2004 revealed that due to corroded and broken water distribution mains, nearly 30% of the drinking water that leaves the water works may never reach the consumer. That number in the United States ranges from 8 to 25%. Appropriate asset condition monitoring would enable inspectors to pinpoint the sites of distribution system leaks. To mitigate and control corrosion in water system components properly, various methodologies have been successfully developed and implemented. These include proper material and coatings selection, water treatment, and use of cathodic protection. Proper application of each methodology can greatly improve the corrosion resistance of water components, reduce the introduction of detrimental elements into the water, improve the components' corrosion resistance, and increase the components' useful life. Using these methodologies in combination has a synergistic affect.

Next Steps

In developed countries, these outlined issues still plague its citizenry. In underdeveloped countries throughout the world, basic components, materials, resources, and knowledge are typically in short demand so proper material selection, coating selection, and use of other corrosion-control techniques are critical to the life cycle of any infrastructure component and health of the consumer.

First and foremost, engineers must understand the limitations in underdeveloped countries such as the availability of materials, coatings, and other corrosion mitigation technologies. Engineers must be cognizant that if components fail, replacements may be delayed for months or more due to availability or access to the facility. If critical components in a treatment facility or distribution system fail due to corrosion, the entire treatment system or water distribution could be critically impacted, resulting in significant health issues.

The availability of simple items can, and will, impact underdeveloped countries in their pursuit to implement safe and sustainable water to their constituents. Corrosion engineers need to think out-of-the-box to prevent—or at least minimize—corrosion-related failures and improve the health and well-being for those in need of a clean and healthy water supply.

Look to AMPP for water industry corrosion control solutions.

Source: Republished with permission from AMPP's Water Corr News; article authored by Jean Broge.  

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