Corrosion in pipelines is one of the major challenges faced by oil and gas industries all over the world. This has made corrosion control or management a major factor to consider before setting up any industry that will transport products via pipelines. In this study the types of corrosion found on system 2A pipeline were; pitting, microbial, sulfide-stress cracking, hydrogen-stress cracking and hydrogen-induced cracking and these were caused by poor maintenance of the pipeline system, severe mutilation of the pipeline coatings, substrates due to vandalization and coating failures. The data from cathodic protection control method from Nigeria National Petroleum Corporation (NNPC)/ Pipeline and Product Marketing Company (PPMC) for system 2A line was analyzed and it was deduced that about 10.3km of the pipeline was well protected and possibly fit for use and about 62.7km is experiencing under protection which means corrosion is predicted to take place in that segment in a short time and finally about 16km of the pipeline is experiencing corrosion. From the results obtained, it can be deduced that the use of cathodic protection technique as a method of controlling corrosion in oil and gas pipelines is effective and efficient when compared to other methods and thus constant monitoring is needed to achieve optimum efficiency.

Weight loss, polarization, and open circuit potential methods were used to investigate the corrosion inhibitory impact of Centrosema pubescens leaf extract on 304L austenitic stainless steel UNS S30403 in 1 M hydrochloric acid. This non-toxic extract behaves as a mixed-type inhibitor according to the polarization curves, thermodynamics and activation parameters. Both the weight loss calculations and potentiodynamic polarization investigations showed that 1.2 g L-1 was the optimal concentration of the leaf extract. While the weight loss method gave inhibition efficiency of 86.84 and 75.00 % after 10 and 60 days of immersion at the optimum concentration, polarization studies revealed inhibition efficiencies of 93.08 and 98.66 % at 303 and 333 K, respectively. The extract molecules adhered to the UNS S30403 surface according to Langmuir adsorption isotherm. The presence of the protective film on the UNS S30403 surface was confirmed by SEM, EDX, and XRD measurements. The inhibition performance of the leaf extract was noted to be a function of the extract concentration, immersion time and temperature. The FTIR analysis indicated an interaction between austenitic stainless steel UNS S30403 and the molecules of Centrosema pubescens leaf extract.