Seawater tests are common when testing corrosion. Seawater is very corrosive because it rusts metal, including the steel bars that often reinforce concrete. These tests involve attaching pieces of concrete to constructions extending over the sea such as piers and oil rigs. Strong waves impact concrete, causing cracks that allow seawater to reach inside a structure and corrode it.
Accelerated testing is common when measuring corrosion. This method involves exposing concrete to more corrosive materials than are normally present in the environment. Accelerated testing allows researchers such as civil engineers to quickly determine whether a concrete structure is able to withstand damage over a long period of time. Seawater is used for accelerated testing, as well as deicing solutions.
Sound waves are used to measure corrosion in concrete. This process is called acoustic monitoring. It operates similarly to the sounds made by a bat to detect cave walls in the dark. A device emits sound waves which bounce off the concrete structure. A recording device detects the returning sound waves, providing an image of the concrete, including cracks and chips in the material. Sound waves do not require extracting a sample of the concrete to perform tests, and sound tests can measure corrosion at a distance which is helpful for large structures such as dams and bridges.
Electric fields produced by the metal bars reinforcing concrete are measured in corrosion tests. Variation in the electric field measured at different locations across the concrete signals that the metal bar reinforcing it has rusted. According to the University of Texas, this method is less reliable because other substances coating the concrete interfere with electrical conduction, and it does not provide information on the rate of corrosion, only the total damage that is already present.
Corrosion inhibitor tests provide information on which substances protect the steel bar reinforcing the concrete from corrosion. Coating the steel bar with a waterproof substance prevents seawater and other liquids from contacting the metal and rusting it. The corrosion-inhibiting substance creates a protective film that covers the rebar. Corrosion tests measure the durability of this protective film, including mechanical as well as chemical resistance.