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Proceeding Paper

Corrosion Protection of Carbon Steel Using Natural Seaweeds from Seawater †

1
Inorganic Chemistry, Physical Chemistry and Electrochemistry Department, Faculty of Applied Chemistry and Materials Science, University Politehnica of Bucharest, 1-7 Polizu St., 011061 Bucharest, Romania
2
Analytical Chemistry and Environmental Engineering Department, Faculty of Applied Chemistry and Materials Science, University Politehnica of Bucharest, 1-7 Polizu St., 011061 Bucharest, Romania
3
The National Institute for Research & Development in Chemistry and Petrochemistry -ICECHIM, Splaiul Independentei no.202, 6th district, P.O. 35-174, 060021 Bucharest, Romania
*
Author to whom correspondence should be addressed.
Presented at the Virtual Eurachem Workshop 2020—“Quality Assurance for Analytical Laboratories in the University Curriculum”, 14–15 July 2020; Available online: https://eurachem2020.ro/.
Proceedings 2020, 55(1), 1; https://doi.org/10.3390/proceedings2020055001
Published: 17 September 2020

Abstract

:
The aim of this work was to investigate the corrosion inhibition effect of natural seaweeds in seawater on carbon steel. The corrosion efficiency of carbon steel in the absence and the presence of natural seaweeds in seawater was evaluated by the gravimetric method at room temperature and calculating the corrosion rate and protection degree. The experimental results showed that the corrosion rate on carbon steel decreased when the seaweeds were used. In addition, the value of protection degree (P) was greater than 60% when seaweeds were used. Natural seaweeds reduce the corrosion rate and can be considered an ecofriendly corrosion inhibitor for carbon steel.

1. Introduction

Corrosion of different metals such as carbon steel, iron, boron steel, aluminum is caused by the chemical interaction with their corrosion medium [1,2,3,4,5].
Today, the various extracts of petals, leaves, peels, seeds, or roots have been used as ecofriendly and effective corrosion inhibitors in different corrosion media [1,2,3,4]. Seaweeds are plants (marine macroalgae) that grow abundantly in the shallow waters of sea, estuaries, and backwaters [5]. The natural extracts have many advantages such as having excellent anticorrosive activity, nontoxicity and biodegradability, and can be extracted by simple methods at low cost [1,2,3,4,5].
The research in the field of “green” corrosion inhibitors shows that the inhibitors, when added in a small concentration into a corrosion medium, reduce the corrosion rate of the exposed metal to that medium. Inhibitors can also alter the corrosive medium into a noncorrosive or less corrosive medium through their interaction with the other species. This occurs depends on the composition of the inhibitors or their corrosive medium. Due to the interaction of inhibitors with the metal surface, a passive film is form that protect the metal from corrosion attack [1,2,3,4,5,6]. In addition, the green corrosion inhibitors are nontoxic, biodegradable, ecofriendly, and do not contain heavy metals or other toxic compounds [4,5,6,7,8,9].
Deyab [5] studied the inhibition effect of seaweed extract on the corrosion of mild carbon steel in saline formation water. The data exhibit that the inhibition efficiency increases with increasing extract concentration, while the corrosion rate decreases with extract concentration. It was found that the seaweed extract can reduce the corrosion rate of mild carbon steel in saline formation water by approximately 93% [5].

2. Materials and Methods

Samples of natural seaweeds and seawater used for the corrosion tests were taken from the Tsarevo area, southern Bulgaria, and used without any purification or filtration. Small plates of carbon steel (10 × 15 mm) were used for corrosion tests, polished using silicon carbide grinding paper with grit P400, degreased with sodium carbonate, rinsed in distilled water, and dried with ethanol. After that, the samples were weighed accurately using an analytical balance (Kern KB, KERN & SOHN GmbH, Balingen, Germany). They were then suspended entirely in glass vessels that contained 25 mL of seawater, without and with natural seaweeds (10 g) (Figure 1). The corrosion experiments were examined by the gravimetric method for 7 days at room temperature (22 ± 2 °C) using one sample for each test. After the corrosion time ended, samples were taken out, washed with distilled water, dried at room temperature, and weighed accurately.
The surface morphology of the carbon steel, before and after corrosion tests, was examined using a digital optical microscope (MT4096, USB, Media-Tech, Bratislava, Slovakia, magnification 300×).

3. Results

To evaluate the corrosion efficiency of carbon steel in the absence and the presence of natural seaweeds in seawater, corrosion rate and protection degree were calculated.
Corrosion rate (CR, g/m2 h) for the samples was calculated by Equation (1) [7,8]:
CR = w i w f A · t   ×   100 ,
where: CR—corrosion rate (g/m2 h); wi—initial weight of carbon steel coupon (g); wf—final weight of carbon steel coupon (g); A—area of the coupon of carbon steel (m2); and t—corrosion time (h).
The protection degree (P) was calculated using Equation (2) [7,8]:
P = C R i   C R f C R i   ×   100 ,
where: CRi—corrosion rate in the absence of seaweeds and CRf—corrosion rate in the presence of seaweeds (g/m2 h).
The values of corrosion rate (CR) and protection degree (P) obtained by weight loss data are presented in Table 1.
The surface morphology of carbon steel samples was examined in the absence and the presence of natural seaweeds in seawater (Figure 2).

4. Discussion

The results presented in Table 1 indicate that the best value of P (66.60%) was obtained in the corrosion medium of seawater with natural seaweeds.
The surface morphology images show that the corrosion reaction does not take place homogeneously over the surface of carbon steel in the absence of natural seaweeds in seawater (Figure 2). In comparison with the surface exposed in the presence of natural seaweeds in seawater, the surface of carbon steel was damaged by the lack of natural seaweeds. It can be seen that seaweeds protected the surface of carbon steel remarkably well in comparison to the solution without seaweeds [7,9].

5. Conclusions

The results show that the corrosion rate calculated by the gravimetric method of carbon steel in seawater decreased when natural seaweeds were used.
The value of protection degree (P) was greater than 60%, after 7 days, when natural seaweeds were used in the seawater. Also, the natural seaweeds reduce the corrosion rate and can be considered as a suitable inhibitor for carbon steel in seawater.
The morphological image of the surface carbon steel plate shows that the seaweeds protect the carbon steel surface.

Author Contributions

Conceptualization, S.C. and A.M.D; methodology, S.C., C.M., and V.P.; resources, S.C. and A.M.D.; funding acquisition S.C. and A.M.D.; formal analysis, C.M.; investigation, S.C., A.M.D., C.M., and V.P.; data curation, S.C., A.M.D., C.M., and V.P.; supervision: S.C. and A.M.D.; writing—original draft preparation, S.C. and A.M.D.; writing—review and editing, S.C., A.M.D., C.M., and V.P. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the University POLITEHNICA of Bucharest, through the UPB-GEX2016, project no. 62/2016, and supported by a grant of the Romanian Ministry of Research and Innovation, PCCDI – UEFISCDI, project no. PN-III-P1-1.2-PCCDI-2017- 0428, within PNCDI III (no.40PCCDI/2018, PC4-FOTOMAH).

Conflicts of Interest

The authors declare no conflict of interest.

References

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Figure 1. The glass vessels that contain seawater, without (A) and with natural seaweeds (B).
Figure 1. The glass vessels that contain seawater, without (A) and with natural seaweeds (B).
Proceedings 55 00001 g001
Figure 2. Surface morphology images of the carbon steel: blank (S1); immersed in seawater without natural seaweeds (S2); immersed in seawater with natural seaweeds (S3).
Figure 2. Surface morphology images of the carbon steel: blank (S1); immersed in seawater without natural seaweeds (S2); immersed in seawater with natural seaweeds (S3).
Proceedings 55 00001 g002
Table 1. The values of CR and P for samples of carbon steel in the different corrosion media.
Table 1. The values of CR and P for samples of carbon steel in the different corrosion media.
Corrosion MediumCR (g/m2 h)P (%)
seawater0.2012-
seawater without natural seaweed0.119440.66
seawater with natural seaweed0.067266.60
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MDPI and ACS Style

Căprărescu, S.; Dăncilă, A.M.; Modrogan, C.; Purcar, V. Corrosion Protection of Carbon Steel Using Natural Seaweeds from Seawater. Proceedings 2020, 55, 1. https://doi.org/10.3390/proceedings2020055001

AMA Style

Căprărescu S, Dăncilă AM, Modrogan C, Purcar V. Corrosion Protection of Carbon Steel Using Natural Seaweeds from Seawater. Proceedings. 2020; 55(1):1. https://doi.org/10.3390/proceedings2020055001

Chicago/Turabian Style

Căprărescu, Simona, Annette Madelene Dăncilă, Cristina Modrogan, and Violeta Purcar. 2020. "Corrosion Protection of Carbon Steel Using Natural Seaweeds from Seawater" Proceedings 55, no. 1: 1. https://doi.org/10.3390/proceedings2020055001

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