**2. Corrosion problems in oil and gas pipeline**

Corrosion is the main problem affecting oil and gas pipelines. Understanding the electro-chemical nature of corrosion was a major breakthrough, as shown in **Figure 1**, and this made it possible for corrosion to be mitigated, if electric current sufficient to offset the inherent corrosion current of a particular environment were caused to flow in the opposite direction. The applied direct current was termed "cathodic" protection because it made the pipe the cathode in a galvanic cell [10, 11]. The required current could be supplied by connecting a "sacrificial" anode (i.e., a metal with a higher oxidation potential than iron) in an electrical circuit where soil acted as the "electrolyte." Alternatively, commercial current could be directed to the pipe via an anode bed. The application of coating and inhibitors also help to solve the corrosion problem [10, 11].

## **2.1 Internal corrosion in pipeline**

Internal corrosion in oil and gas pipelines is primarily caused by the presence of water together with acid gases (carbon dioxide or hydrogen sulphide) or sulphate reducing bacteria [12]. It can be divided into three broad categories:

• Sweet corrosion

*Corrosion Inhibitors*

corrosion are put into use.

peels, Tobacco leaves, etc. [1, 3–5].

dumped cassava waste.

as proper material selection, cathode protection (CP) and application of inhibitors to modify the corrosive environment. In time past different types of coatings have been used such as bituminous enamels, asphalt mastic, liquid epoxies and phenolics, extruded plastic coatings, fusion-bonded epoxy (FBE), tape, threelayer polyolefin, wax coatings, high performance composite coating system, low temperature application technology for powder, thermotite flow assurance coating technology and paint. Paints used as coatings have been very effective in reducing the rate of corrosion in many industries, where various metals which are prone to

Use of some inhibitors, such as chromate, has been banned because of toxicity and the environmental hazards they create [1]. Hence there is a need to make use of environmental friendly, non-toxic extracts of naturally occurring plant materials as corrosion inhibitors also known as green corrosion inhibitors. Extracts of plant materials contain a wide variety of organic compounds. Most of them contain hetero-atoms such as phosphorous, nitrogen, sulfur and oxygen. These atoms coordinate with the corroding metal atom (their ions) through their electrons [2]. Hence protective films are formed on the metal surface, thereby preventing corrosion. Some of the green corrosion inhibitors that have been used in the past are extracts from Aloe vera, Banana Plant juice, Mango, Orange, Passion fruit, Cashew

Most researches have led to the discovering of new green corrosion inhibitors from plant part, but few of them have provided practical coating application that can solve corrosion problems as it applies to the oil and gas pipelines. Most green corrosion inhibitors are extracted from food and fruit items e.g. mango, orange, cassava, cashew juice and bitter leaf, which endangers food security. It is important to identify the ingredients and nature of bonds that exist in plant part extracts which are responsible for inhibiting corrosion in steel pipelines. The use of liquid extracts from cassava tuber has been studied in the past for corrosion resistance for mild steel [6]. But there is still work to be done in the area of coating using green inhibitors. Cassava plant solid extract (bark, stem and leaf) which are dumped in the environment can be processed and used as corrosion inhibitors because of the presence of heteroatoms and organic compounds, which are responsible for inhibiting corrosion. Processing of cassava plant solid extract (bark, leaf and stem) into green corrosion inhibitor will provide a cheap, environmental friendly and efficient green corrosion inhibitor and also solve environmental challenges caused by the

Paint which usually consists of four main parts includes: solvents, pigments, binders and additives. In dealing with anticorrosive paints, red oxide pigment helps in preventing corrosion. The additives in paints play vital roles, which include the inhibition of corrosion. Inhibitors can be added to paint and it must be non-toxic, environmentally friendly, cost effective and readily available. Extracts from plants have been used as green inhibitors in the past and have been found to be environmentally friendly, non-toxic, cheap and abundantly available. Nanoparticles can improve paint property because of the unique properties of nanoparticles. Incorporating nanosize additives in paint provide effective barrier performance, reduce the amount of holiday in paint and also enhance the integrity and durability of paint, since the fine particles dispersed in paint can fill cavities. Research has been carried out on cassava starch as green corrosion inhibitors [7], and the modification of cassava starches as potential corrosion inhibitors has been used on steel rods. Cassava starch which is sometimes a waste in most cassava processing plants,

shows considerable improvement in the prevention of corrosion [8].

This current chapter seeks to discuss green corrosion inhibitory potentials of cassava plant (*Manihot esculenta Crantz*) extract nanoparticles (CPENPs) in

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#### **2.2 External corrosion in pipeline**

The medium in the surrounding reacts with the outer side of metal pipelines chemically, electrochemically and physically causing certain damages. These damages are called external corrosion of pipelines. The soil is complex three-phased

**Figure 1.** *Schematic of anodic site and cathodic site as they lead to corrosion [9].*

system, which makes it a conductor to the metal pipelines. Plus, the oxygen concentration cell caused by the oxygen concentration difference accelerates the pipeline corrosion [13].

