Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 (CC BY 4.0) International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. Abstract: Subsea transmission pipelines (STP) are designed to transport liquids, gases or solid/liquid mixtures over some distances. STP are buried underground or submerged in water for transportation of natural oil and gas (O&G) products. A Vernonia amygdalina (VA) solution is prepared to act as an inhibitor. The specimens are kept in a workable state. Steps are taken to prepare each specimen. All cuts and sheared edges were ground out to prevent them from becoming sites for preferential attack. The finishing of the specimen surface with grit abrasive paper (sand paper) and rinsing of the specimens in distilled water are carried out. Then, degreasing of specimen in acetone and air-dried are carried out. Upon drying, the specimens are immediately weighed to obtain their initial weights. Twelve specimens are used for the test as follows: 6 Aluminum (Al); and 6 mild steel (MS) samples. With a 2M concentration of VA solution, the MS and Al samples are immersed in different plastic containers containing 400ml of seawater with pH value of 7.25 with no (0%) inhibitor added to it. A 5% (400ml) of the VA solution is poured into the measuring cylinder for each sample-Al and MS. The specimens are suspended by the strings and completely immersed in the different percentage test media. The same procedure is carried out for each of the different percentages (i.e. 10%, 15%, 20%, and 25%) and a total of 12 solutions are set up. The seawater used has 7.25 pH. At the end of every week (168 hours), the specimens are removed from the corrosive media. Observation and recording of appearance of the specimen, noting sites are done to analyze the effect of the VA solution on the AL and MS used for the STP. Values are obtained and graphs plotted on weight loss (WL) and corrosion rate (CR) versus the time. It is observed that the VA solution has different effect on the STP at different time and percentage of the VA solution introduced into the environment of the pipe. It was also observed that optimum inhibition of coupons is obtained between 15-25% of VA solution during the first four weeks of testing. At the fifth week, the inhibitor was gradually losing its effectiveness. This means that more inhibitor needs to be added at regular intervals in order to sustain the effectiveness of the inhibitor.

Pipelines are system of pipes designed to transport liquids, gases or solid/liquid mixtures over long distances. Some are used for domestic, household and sewage purposes. Others are buried underground or submerged in water for transportation of natural oil and gas (O & G) products. In this work, the specimens had to be kept in a workable state and steps were taken to prepare each specimen: all cuts and sheared edges were ground out to prevent them from becoming sites for preferential attack. The finishing of the specimen surface with grit abrasive paper (sand paper) and rinsing of the specimens in distilled water were done. Then degreasing of specimen in acetone and air-dried were carried out. Upon drying, the specimens were immediately weighed to obtain their initial weights. Twelve specimens were used for the test as follows: 6 Aluminum (Al); and 6 mild steel (MS) samples. With a 2 M concentration of Vernomia Amydalina (VA) extract solution, the MS and Al samples were immersed in different plastic containers containing 400 ml of seawater with pH value of 7.25 with no (0%) inhibitor added to it. A 5% (400 ml) of the VA solution was poured into the measuring cylinder for each sample-Al and MS. The specimens were suspended by the strings and completely immersed in the different percentage test media. The same procedure was carried out for each of the different percentages, 10%, 15%, 20%, and 25% and a total of 12 solutions were set up. The experimental procedure used was that seawater of 7.25 pH was obtained from Abonnema water front of Rivers State. At the end of every week (168 hours), the specimens were removed from the corrosive media. Observation and recording of appearance of the specimen noting sites were done. Cleanings of specimen with white handkerchief or tissue paper were carried out and washing of specimen with distilled water, scrubbing of specimen with a soft brush and dipping the spe