This paper presents an experimental investigation that correlates the oxygen diffusion coefficient to the corrosivity of distinct Saudi Arabian soil types under various degrees of saturation (Sr). The corrosivity of the soils were assessed using electrochemical techniques including open circuit potential, electrochemical impedance spectroscopy, and potentiodynamic polarization while the effective oxygen diffusion coefficients (De) of the soils were obtained using a dual-chamber experimental setup coupled with an analytical model based on Fick's laws. The experimental results revealed corrosion severity to be strongly underpinned by Sr and De. All soil types exhibited a distinct critical Sr ∼ 0.75 at which the corrosion rate is maximized.
Buried steel pipelines operating in soil environments are constantly under threat from corrosion, a phenomenon which jeopardizes their structural integrity and escalates the risk of material degradation, leakage, and subsequent environmental hazards. A holistic understanding of the corrosion process in soil environments is essential for strengthening infrastructural resilience and upholding environmental sustainability.
Corrosion of metals in soils is dictated by a complex confluence of several factors, including aeration, pH, moisture content, ionic composition, electrical resistivity, and microbial activity1. Among these elements, soil moisture, typically represented as the degree of saturation (Sr), is a key determinant of corrosion in soils2. Its pivotal role emerges from its impact on several corrosion-related processes, including electrical conductivity3, oxygen diffusion4-5, and interfacial characteristics5-7.
Although soil resistivity has been widely used to predict corrosion in buried pipes, inconsistencies are frequently reported between theoretical predictions and actual observations7-8. These discrepancies suggest that soil resistivity alone is an insufficient predictor of corrosion, highlighting the need to consider other influential parameters such as oxygen diffusion and moisture content2.
The degree of saturation (Sr) offers a measure of soil moisture content, defined as the ratio of volume to the total void space within the soil matrix. This metric is influenced by various factors including the soil's structural makeup, pore space configuration, prevailing moisture levels, and compaction degree, as gauged through parameters like soil density and porosity.
