PSI - Issue 36

Tetyana Kalyn et al. / Procedia Structural Integrity 36 (2022) 313–317 T. Kalyn, L. Poberezhny, P. Popovych et al. / Structural Integrity Procedia 00 (2021) 000 – 000

314

Inhibitory protection is one of the most effective and uncomplicated technology for ensuring the integrity of pipelines, which complements the measures for the reconstruction and replacement of pipelines. There are a number of inhibitors used in an acidic environment in the gas and oil industry (Bereket et al. (2002 ), Finšgar et al. (2014) and others), however the toxicity of synthetic organic compounds limits their usage. Therefore, recent researches are focused on development of green corrosion inhibitors (Slobodian et al. (2021)). The use of vegetable raw materials is promising for the creation of anti-corrosion agents. Plant extracts contain natural compounds that are biodegradable, cheap and environmentally friendly. There are numerous studies on plant extracts as corrosion inhibitors, mainly in acidic solutions (Al-Otaibi et al. (2014), Alaneme et al. (2016), Umoren et al. (2016), Qiang et al. (2018), Liao et al. (2018)). Some vitamins also exhibit anti-corrosion properties, as they contain the necessary electronic structural characteristics of inhibitors – heteroatoms, the system of conjugated bonds (Chidiebere et al. (2015)). They are environmentally friendly and cheap. Investigations carried out by Nigam et al. (1990), Ferreira et al. (2004), Valek et al. (2008), Chidiebere et al. (2015), Hong et al. (2016) demonstrated that ascorbic acid (AA) being the water-soluble vitamin protected steels against corrosion. The low alloy 17H1S steel is widely used in the oil and gas industry. There are many investigations devoted to solving the problems of corrosion and corrosion protection of the structures made of the low alloy pipeline steels (Ossai et al. (2016), Poberezhny et al. (2017a, 2017b, 2018, 2019a, 2019b), Maruschak et al. (2018), Nykyforchyn et al. (2019), Wang et al. (2020), Deng et al. (2021), Zvirko et al. (2021) and others). Therefore, seeking for effective and environmentally friendly inhibitors for protection of low alloy pipeline steels against cororrosion in the oil and gas industry is very important. This study aims at investigating the effectiveness of using of AA as green inhibitor for protection of the low alloy 17H1S pipeline steel against corrosion in near-neutral soil electrolytes. 2. Materials and methods The low alloy 17H1S steel was investigated. The chemical composition of the steel is presented in Table 1. The studies were performed in the NS4 solution, simulating soil environment, of the following composition: KCl – 0.122 g/l, NaHCO 3 – 0.483 g/l, CaCl 2 ∙ 2H 2 O – 0.181 g/l, MgSO 4 ∙ 7H 2 O – 0.131 g/l.

Table 1. Chemical composition of 17H1S pipeline steel С Si Mn Ni S

P

Cr

Cu

Fe

0.14-0.20

0.40-0.60

1.00-1.40

≤ 0.30

≤0.035

≤0.030

≤0.30

≤0.30

>97

Protective properties of the corrosion inhibitor were studied using weight loss method. Samples were maid of the 17H1S steel with dimensions of 50x10x3mm. They were degreased, dried, and weighed using an analytical weight with an accuracy of 0.0001 g. Three parallel tests were carried out. Corrosion rate W was determined by the formula:

1 2 W m m S  − =

(1)

,

where m 1 and m 2 – the mass of the sample before and after testing, respectively, g; S – area of the sample, m 2 ; τ – exposure time, hours. The results are presented as the mean value of three parallel tests. The degree of protection of the steel against corrosion IE w was determined by the formula:

W W −

(2)

(%)

%

IE

100

=



0

W

0

where W 0 and W – corrosion rate of steel in test solution without and with inhibitor, respectivelly. Electrochemical tests were performed using a MTech COR-410 potentiostat by polarization method. Voltammograms were measured within the electrode’s potential within the range of -1.6...+ 0.3 V. Potential sweep