Corrosion is a chemical or electrochemical reaction that causes degradation of a material. The environment plays an important role in the extent, type, and severity of corrosion. Underground corrosion involves structures that are buried or otherwise surrounded by soil—for example, storage tanks and pipelines. Often, these structures store and transport oil, gas, and other hazardous substances, which if released to the environment, can cause substantial damage. Severe corrosion of buried metal structures has led to explosions, loss of life, and massive environmental clean ups. In addition, leaking water pipes may cause or contribute to landslides and other earth movement. The direct cost of corrosion in the United States was estimated in 2001 to be $279 billion annually, while the direct cost of corrosion associated with underground storage tanks (USTs) alone was estimated to be $2.5 billion annually.
Due to extraction and processing, most metals and alloys are thermodynamically unstable. Metallic corrosion occurs because metals and alloys want to revert back to their native, stable states. For example, iron and steel corrode to form a corrosion product commonly known as rust. Underground corrosion can manifest itself in a number of ways, from uniform thinning of a tank or pipe wall to very localized pitting corrosion. The type of corrosion will depend on the particular metal and the nature of the soil environment. Microbiological and galvanic corrosion (or dissimilar metal corrosion) can also play a role. The corrosivity of a specific soil depends on many factors; two keys are moisture content and degree of aeration. Other factors can also play an important role, such as pH, the presence of contaminants, permeability, chloride and sulfate content, and the presence of micro-organisms.
With 40 years of experience in solving complex scientific and engineering problems, Exponent is uniquely qualified to lead underground corrosion investigations. Because our soil engineers and geologists can draw on our in-house expertise in the areas of metallurgy, electrochemistry, and mechanical engineering, Exponent can provide a multi-disciplinary approach that will solve any underground corrosion problem.
Our services include:
- Site inspection and sample collection
- Laboratory testing
- Creating and examining metallurgical mounts
- In-house Energy Dispersive Spectroscopy (EDS)
- In-house Scanning Electron Microscope (SEM)
- Analysis and interpretation of soil and water chemistry data
- Analysis of the cause(s) of corrosion
Exponent engineers and scientists have experience in the investigation of damage due to corrosion for small- and large-scale projects.