Corrosion Inhibitors used in Pipelines Carrying Simulated Oil Well Water – An Overview and Inhibition of Corrosion of Mild Steel in Simulated Oil Well Water by Aqueous Extract of Chrysanthemum Indicum Flower- Case Study

Simulated oil well water (SOWW) is conceded out by pipelines made of several alloys for instance mild steel & L80. These alloys may undergo corrosion owing to presence of various aggressive ions present in SOWW. To prevent this several inhibitors have been used. Several methods have been used to estimate inhibition efficiency of extract. Weight loss study, electrochemical study like potentiodynamic polarization study & electrochemical impedance spectroscopy study, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), nuclear magnetic resonance spectroscopy (NMR), atomic force microscopy (AFM) and TEM have been employed in these studies. Recent developments in this field of research is presented in detail briefly. As a study Inhibition of corrosion of mild steel in simulated oil well water by aqueous extract of Chrysanthemum indicum flower is also discussed. CONTACT S Rajendran susairajendran@gmail.com Department of Chemistry, Corrosion Research Centre, St. Antony’s College of Arts and Sciences for Women Thamaraipady, Dindigul–624005, TamilNadu, India. © 2021 The Author(s). Published by Oriental Scientific Publishing Company This is an Open Access article licensed under a Creative Commons license: Attribution 4.0 International (CC-BY). Doi: http://dx.doi.org/10.13005/OJPS06.01-02.07 Oriental Journal of Physical Sciences www.orientaljphysicalsciences.org ISSN: 2456-799X, Vol.06, No.(1-2) 2021, Pg. 36-43 Article History Received: 10 September 2021 Accepted: 02 November 2021


Introduction Simulated Oil Well Water
Simulated oil well water (SOWW) is carried out by pipelines made of several alloys. These alloys undergo corrosion owing to presence of various aggressive ions present in SOWW. To prevent this several inhibitors have been used. Many researches have been carried out in this regard. [1][2][3][4][5][6][7][8][9][10] Metals Some inhibitors have been used to thwart corrosion of many metals like N80 carbon steel alloys, 1 API 5LX carbon steel, 2 X80 pipeline steel, 3 X-65 type carbon steel, 4 mild steel, 5-7 metallic S90 steel 8 and carbon steel. 9,10 Medium Inhibition efficiency of extracts in scheming corrosion of metals in various environments has been investigated. The medium includes HCl, 1 oil well produced water, 2 oil field waters, 3 oil well formation water, 4 simulated oil well water, 5-7 oil fields, 8 produced water in acidizing oil wells 9 and 15 % HCl. 10
Results are abridged in Table 1.

Results & Discussion
A green corrosion of an aqueous extract of Chrysanthemum indicum flower (CIF) has been applied to regulate corrosion of mild steel in existence of simulated oil well water (SOWW). Findings will be expedient in petroleum technology. These inhibitors may be included to oil well water conceded by pipelines made of mild steel.

Weight Loss Method
Inhibition efficiency (IE %), corrosion rate (CR) & surface coverage (θ) values was premeditated from weight loss method 16 for mild steel with nonexistence & existence of various concentrations of (CIF) at room temperature are abridged in Table 2. From  There are several isotherms proposed to account for adsorption of corrosion inhibitor molecules on surface of metal. From isotherm, linear relationship between θ and concentration of inhibitor can be found. In this study, the changes in the θ and thereby the change in the efficiency of inhibitor is determined by using different isotherm model.

Langmuir Adsorption Isotherm
Degree of surface coverage (θ) for innumerable concentrations of inhibitor (2, 4, 6, 8, 10 ml) at room temperature was found from the weight loss method. According to Langmuir isotherm, the following equation relates the surface coverage (θ) and inhibitor concentration, C.
...(4) The plot of Langmuir adsorption isotherm, C/θ vs C shown in Figure 1. Values of adsorption parameters obtained from Langmuir adsorption isotherm including ∆G 0 ads , R 2 , slope and intercept of inhibitor on mild steel surface are listed in Table 3. Negative sign of ∆G 0 ads make sure extemporaneity of adsorption process & constancy of adsorbed layer on steel surface. ∆G 0 ads is premeditated from equation.
∆G 0 ads = -2.303 RT log (K ads x 55.55) ...(5)  The R 2 value was very high 0.9911. The negative value of Gibb's free energy approves that adsorption of inhibitor on metal is spontaneous. These interpretations indicates that adsorption of inhibitor molecules on metal surface comply with the Langmuir adsorption isotherm. 19,20

Analysis of Contact Angle Measurement
Contact angle measurement is modest technique for characterization of surfaces. It is useful in explaining the data such as information between a hydrophobic and hydrophilic surface of the metal and surface of the protective film formed. 21 When contact angle increases, hydrophobicity also increases. Because of this, when water repellent nature of surface upsurges & corrosion inhibition efficiency also increases. The contact angle images are shown in Figure 2. Contact angle values of polished metal, metal immersed in corrosive environment (SOWW) It is pragmatic from Table 4, that contact angle for polished metal is precise high (111.6°). For polished metal engrossed in SOWW, the contact angle is precise small (8.9°). For polished metal engrossed in inhibitor system the contact angle is in between that of the above two systems (96.6°). The contact angle measurement study is expedient in explaining hydrophobicity of metal surface & corrosion inhibition efficiency upsurges of inhibitor system. 22-24

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In this study, anti-corrosive property of aqueous extract of CIF has been tested against the mild steel in SOWW medium. • Diminution in corrosion rate & escalation in inhibition efficiency of mild steel in SOWW media was observed with upsurge in concentration of CIF. Maximum inhibition efficiency of 93 % was accomplished for 10 ml of CIF. • Adsorption process tracked Langmuir isotherm model. Negative value of ∆G0ads achieves that adsorption process was extemporaneous.

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Contact angle measurement studies reveal that the inhibitors form protective layer on mild steel surface in SOWW environment.

Funding
The author(s) received no financial support for the research, authorship, and/or publication of this article.