Experimental Investigation of the Effects of Different Environmental Conditions on Pipelines Corrosion Rates

Abstract

An estimate of about $18.5 million are expended by industries in Nigeria yearly on corrosion, the oil and gas industry takes more than 65% of this cost due to the peculiar nature of their facilities and operational conditions. In spite of the use of galvanized pipeline and application of the anti-corrosion coating of crude oil pipeline and other metallic structure in the oil and gas industry, corrosion failures are still daily occurrences. These corrosive failures have been attributed to the environmental conditions in which the pipeline and other metallic structures are located. This research studies the rate of deterioration (corrosion rate) of carbon steel pipeline (flow pipe) under five different environmental conditions, coated with different anti-corroding agents, and subjected to different temperatures and pH values. Five Different environmental conditions through which pipelines are laid (Top soil + Fresh water, Sea water bed sand + Sea water, Lagoon water, Seawater, NaCl solution (0.5M)) were simulated in the laboratory. Different seventy gram (70g) samples of the carbon steel pipeline were used as the coupon samples. Red oxide oil paint and tar paint were used as the anti-corroding agents. Water bath was used in regulating the temperature and different concentration of HCL and NaOH were used to vary the pH. Weight loss method was used to calculate the corrosion rates. Results show that carbon steel resists corrosion better when buried in soil than when submerged in water; also the corrosion rate is more in sea water than in the lagoon water of relatively smaller salinity. The rate of corrosion was observed to increase with: increase in temperature, increase in salinity, and increases in acidity and alkalinity. Also the tar paint is more effective as anti-corrodant than the red oxide oil paint when applied to the carbon steel pipeline under same environment conditions. The study successively reduced the corrosion rate of the 70g coupon sample from 0.00127g/day when the sample were suspended in 0.5M, NaCl solution to 0.000104g/day when pipeline coated with tar paint are buried in dry soil.