Corrosion in Water Wells
Part 1. Corrosion mechanisms in water wells.
By Thom Hanna, PG
Figure 1. Oxidation-reduction corrosion cell on a steel surface (Hanna et al. 2016).
Corrosion in water wells typically refers to the gradual deterioration of metallic components such as casings, screens, drop pipes, and pumping equipment. It occurs when metals react with water, dissolved minerals, gases, or microorganisms present in the environment.
Over time, corrosion weakens well structures, reduces pumping efficiency, and can introduce unwanted materials such as rust, sulfides, or sediment into the water. If not properly managed, corrosion may lead to leaks, costly repairs, or total well failure.
More than half of untreated groundwater sources in the United States contain water classified as “potentially corrosive” (USGS 2016). Corrosion is therefore not an anomaly but an inherent, ongoing process that must be actively managed.
Globally, corrosion is estimated to cost water infrastructure operators more than $2.5 trillion annually, representing nearly 3.4% of global GDP (NACE 2019). Beyond mechanical deterioration, corrosion contributes to substantial economic losses and environmental consequences due to increased maintenance costs, resource waste, and contamination risks.
This column—the first of a two-part series—focuses on corrosion mechanisms in water wells. A follow-up in the Water Well Journal April 2026 issue will address material selection and mitigation strategies for reducing corrosion-related failures and extending the life of water wells.
Corrosion Mechanisms in Water Wells
Figure 2. Effect of chlorides and flow rate on corrosion rate (Badrak 2012).
Corrosion in water wells primarily results from electrochemical reactions between metal surfaces and the surrounding environment. These reactions occur because metals tend to revert to a lower energy state by reacting with environmental elements. Electrochemical corrosion involves two simultaneous processes: oxidation, where metal atoms lose electrons and form metal ions, and reduction, where electrons are accepted by a reducing agent, typically oxygen (Hanna et al. 2016).
When different metals or regions of the same metal are immersed in an electrolyte, a galvanic cell forms. The anodic region dissolves into the electrolyte, while electrons travel to the cathodic region, resulting in continuous metal loss (Figure 1).
The corrosion rate depends on factors such as metal type, electrolyte composition, temperature, pH, and flow velocity. Microbiological activity can further modify electrochemical conditions by producing acids or sulfides that accelerate metal loss.
Factors Influencing Corrosion
Figure 3. General corrosion showing uniform rusting and wall thinning on galvanized steel drop pipe (Hanna et al. 2016).
Water chemistry and operating conditions strongly influence the rate and form of corrosion in wells. Water parameters such as pH, chloride concentration, dissolved oxygen, and total dissolved solids (TDS) play critical roles (Badrak 2012a; Badrak 2012b). Low pH water accelerates corrosion by increasing hydrogen ion activity, while high dissolved oxygen promotes oxidation at metal surfaces.
Chloride ions attack protective oxide layers on metals such as stainless steel, leading to localized damage. Similarly, elevated TDS increases electrical conductivity, accelerating electrochemical reactions.
Operating conditions also have a major impact. Elevated temperatures increase ion mobility and reaction rates, whereas high water velocity can strip protective films from metal surfaces (Figure 2), exposing fresh material to further attack. Wells operating in sandy aquifers are especially prone to erosion-corrosion caused by suspended particles.
Common Forms of Corrosion in Water Wells
Figure 4. Deep, localized pits on a stainless steel pump bowl. Even small pits can cause leakage or mechanical failure (Hanna et al. 2016).
Corrosion manifests in several distinct forms, each influenced by environmental conditions, metal type, and operational parameters.
General Corrosion: This uniform attack occurs across the entire surface of a metal when oxygen and water react evenly (Figure 3). Over time, this results in rusting and gradual wall thinning, potentially leading to casing perforation. In well environments, general corrosion is accelerated by acidic conditions
and high oxygen levels. Protective coatings, stainless steel materials, or pH stabilization are effective mitigation measures.
Pitting Corrosion: Pitting corrosion is a highly localized form of attack that results in small but deep cavities or pits (Figure 4). It often occurs when the protective passive layer on metals, especially stainless steels, is breached by chloride ions or mechanical abrasion. A single pit can lead to failure long before surface damage is visible. This type is especially dangerous because it is difficult to detect without close inspection or ultrasonic testing.
Figure 5. Crevice corrosion beneath a threaded coupling where stagnant water created an acidic microenvironment (Hanna et al. 2016).
Crevice Corrosion: Crevice corrosion develops in confined or shielded areas such as under gaskets,washers, or threaded joints where stagnant water limits oxygen diffusion (Figure 5). The oxygen-depleted environment becomes acidic, creating a microcell that accelerates corrosion. It is common under screen jackets and threaded couplings in drop pipe assemblies. Welding joints or using non-threaded connections
help prevent this issue.
Galvanic Corrosion: When two dissimilar metals come into contact in the presence of an electrolyte, a galvanic cell is established. The less noble metal (e.g., carbon steel) acts as the anode and corrodes preferentially to protect the more noble one (e.g., stainless steel or bronze) (Figure 6). In wells, this commonly occurs at interfaces between carbon steel casing and stainless steel pumps or screens. Using similar metals or insulating fittings minimizes galvanic interaction.
Figure 6. Galvanic corrosion between stainless steel and carbon steel showing localized attack on the less noble metal (Hanna et al. 2016).
Cavitation Corrosion: This form occurs in pumps and impellers when pressure drops cause vapor bubbles to form and collapse violently, damaging the metal surface (Figure 7). The impact removes coatings and roughens surfaces, creating initiation points for further corrosion. Proper pump submergence, avoiding air entrainment, and maintaining stable flow reduce cavitation damage.
Flow-Accelerated and Erosion-Corrosion: In high-velocity systems, protective oxide films are worn away by flowing water or suspended solids, exposing fresh metal to attack (Figure 8). This combined mechanical and chemical process is especially prevalent in wells with sandy aquifers or high discharge rates. Flow control and material selection, such as abrasion-resistant coatings, help mitigate this form.
Figure 7. Cavitation pits on a pump impeller caused by collapsing vapor bubbles (Grainger 2023).
Microbiologically Induced Corrosion: MIC results from biological activity, particularly by sulfate-reducing bacteria (SRB) that produce hydrogen sulfide. These bacteria form biofilms that trap water, create oxygen-deficient zones, and secrete corrosive byproducts that promote pitting (Figure 9). MIC is especially common in stagnant or intermittently used wells. Regular disinfection, biocidal treatment, and brushing are effective control measures.
Discussion
Figure 8. Erosion-corrosion on steel pipe caused by high flow velocities and entrained sand particles (ICorr 2023).
Corrosion in wells is a complex interaction between chemical, mechanical, and biological factors. Although inevitable, understanding the interplay of these mechanisms allows engineers to manage and mitigate its effects. Comparative studies show that wells in saline aquifers tend to experience higher rates of pitting and galvanic corrosion, whereas those in low-flow, iron-rich environments are more prone to MIC and general
corrosion.
Effective corrosion management integrates material selection, monitoring, and operational control. Selecting materials compatible with groundwater chemistry, avoiding dissimilar metal contact, and regulating flow conditions are fundamental.
Figure 9. Microbiologically induced corrosion showing pitting under bacterial biofilm deposits (Hanna et al. 2016).
Continuous monitoring through water quality testing and monitoring of the well as outlined in the Operational Stage of the Well (Hanna et al. 2016) can help in monitoring the health of the well and extend the well life.
Corrosion significantly impacts well performance, safety, and long-term costs. It reduces hydraulic efficiency, contaminates water, and increases maintenance demands. To minimize its effects, engineers must combine good design, proper material selection, and ongoing monitoring. Emerging technologies such as smart sensors and advanced coatings offer promising new ways to detect and mitigate corrosion early.
As detailed in Operational Stage of the Well, proactive corrosion management is both sound engineering and responsible resource stewardship. The subsequent article will examine well construction materials and their resistance to corrosion under varying environmental conditions. There will also be a discussion of the selection of materials used in the construction of water wells and their resistance/susceptibility to corrosion in typical water well environments.
References
Badrak, R.P. 2012a. Corrosion and Materials for Water Well Applications. Proceedings of the 3rd International Congress on Water Management in the Mining Industry, Santiago, Chile.
Badrak, R.P. 2012b. Effect of Water Chemistry on Well Corrosion. Santiago, Chile.
Grainger, B. 2023. Cavitation Pits Caused by Vapor Bubble Collapse. Grainger.com.
Hanna, T.M., Schnieders, M.J., and Schnieders, J.H. 2016. Operational Stage of the Well: Evaluating the Forms of Water Well Deterioration and Developing Corrective Actions. National Ground Water Association Press, Westerville, OH.
ICorr. 2023. Flow-Accelerated Corrosion – Synergistic Effects of Influencing Parameters. Sauereisen.com.
NACE International. 2019. International Measures of Prevention, Application, and Economics of Corrosion Technologies (IMPACT) Study. Houston, TX.
U.S. Geological Survey. 2016. All About Corrosivity of Groundwater. USGS.gov.
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Thomas M. Hanna, PG, is a technical director of water well products/hydrogeologist for Johnson Screens where he works in areas of well design, development, and well rehabilitation. He is a registered professional geologist in Arizona, Kentucky, and Wyoming and has worked for several groundwater consulting firms. Hanna can be reached at thom.hanna@johnsonscreens.com.
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