Although soil corrosion is often not visible, its consequences are important for any buried structure.
In addition to its outdoor soil corrosion exposure site, OCAS also has lab set-ups to assess soil corrosion.
For the lab set-up, tubes are filled with different soil and varying moisture content, salts are added to increase corrosion rate. Parameters such as pH, soil texture, resistivity, soil moisture and redox potential are regularly monitored. During the test, samples are evaluated on visual corrosion products, weight loss & pit depth through 3D profilometry and microscopy. The corrosion products are analysed using XRD, FT-IR, SEM-EDX.
The lab test allows to evaluate the buried corrosion resistance for different soil compositions. In that way, different materials and/or soils can be tested and compared. The graph below shows results of the accelerated lab soil corrosion test after 6 months of testing.
Click to enlarge image.
Outdoor soil corrosion exposure site
Samples are tested in different soils: sandy, loam and acidified loam. These are buried at different depths and are regularly evaluated: from a few months to several years.
A clear correlation between corrosion rates from lab and outdoor soils has been found. The combined data from outdoor exposure and accelerated lab exposure experiments allows to make predictions on long term durability of metal structures.
“Corrosion simulation and accelerated testing are essential and crucial to predict the durability of materials. OCAS developed testing methods for soil applications that allow assessing and comparing the corrosion resistance of different samples.”