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Soil Tests Laboratory provides soil corrosivity testing and Corrosion Control Recommendation Reports for buried infrastructure projects. The Full Corrosion Suite measures soil electrical resistivity, pH, sulfates, chlorides, ammonium, nitrates, sulfides and redox potential. Send your project specification, material of concern and sample details to confirm the testing and reporting scope before shipping.
Here at SoilTestsLab we want to help you maximize your material lifespan, and stop early failures that could have been prevented with a little more knowledge.
In general, the corrosion rate of metals in soil depends on the electrical resistivity, the elemental composition, and the oxygen content of the soil.
Different buried materials respond differently to soil conditions. Our Full Corrosion Suite measures properties that can support a corrosion assessment and material-selection review. Soil Tests Laboratory also offers Corrosion Control Recommendation Reports. Interpret the results alongside the proposed material, protective measures, site conditions and project requirements; laboratory results alone do not predict an exact service life or guarantee installed performance.
The Full Corrosion Suite tests for:
Soil Resistivity - Electrical resistivity is one indicator used in a soil corrosion assessment. Lower resistivity can facilitate electrochemical corrosion, but resistivity alone does not establish the corrosion rate for every buried material. Consider the result with soil chemistry, moisture, oxygen conditions and the material or protective system being evaluated.
pH - The pH level of soil drastically effects the corrosion rate of steel, iron, copper and aluminum alloys. Different materials have vastly different performance outcomes under acidic or alkaline environments. It is important for material selection to understand the pH of the soil before installing underground infrastructure.
Sulfates - Sulfate levels in soil effect the corrosion rate of concrete and concrete encased metals. Sulfate-induced corrosion is driven by a combination of electrochemical factors, passive layer disruption, formation of acidic conditions (like sulfuric acid), and microbiologically induced corrosion through sulfate-reducing bacteria. Although sulfates tend to be less aggressive than chlorides in initiating corrosion, they can still significantly accelerate the degradation of metals, especially in acidic or anaerobic environments.
Chlorides - Elevated Chloride levels contribute to accelerating corrosion rates of concrete encased steel (Rebar), as well as just about all metals. Chlorides disrupt the thin protective oxide layer that forms on the surfaces of metals, which leads to corrosion. Chlorides also create tiny anodic regions (active corrosion spots) that dissolve the metal. This process is called “Pitting.” Additionally, Chlorides increase electrochemical activity, and alter the local environment to become more acidic and reactive.
Ammonium - Elevated ammonium levels contribute to the formation of acidic environments when mixed with water. It also contributed to corrosion via the creation of corrosive ammonium salts, stress corrosion cracking in metals like copper alloys, and increases the conductivity of aqueous solutions.
Nitrates - Nitrates can promote corrosion by forming nitric acid, participating in electrochemical reactions, or reducing to more corrosive species like nitrites or ammonia.
Sulfides - Sulfides accelerate metal corrosion through several mechanisms, including the formation of corrosive metal sulfides, promotion of localized corrosion, induction of stress corrosion cracking, and most importantly can indicate the presence of sulfate-reducing bacteria. (SO₄²⁻+organic matter→S²⁻+CO₂)
Reduction-Oxidation Potential (REDOX) - A positive redox potential indicates that the environment is relatively oxidizing. This means that there is a tendency for substances in the environment to be in their oxidized states rather than their reduced states. Sulfate-reducing bacteria thrive in reducing (anoxic) environments where the redox potential is negative. Positive redox values are not conducive to SRBs because these bacteria require low or negative redox conditions to reduce sulfate (SO₄²⁻) to sulfide (H₂S).