Influence of pH on the Inhibiting Characteristics of Cresol Red Incorporated in Chitosan Coatings on Zinc
The present work focuses on the investigation of protective coatings produced on zinc from chitosan (Chit) and an anionic dye, namely cresol red. Cresol red (CR) fulfills the basic requirements to be used as a corrosion inhibitor because it possesses a relatively high molecular weight and includes i...
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MDPI AG
2023-11-01
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| Series: | Metals |
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| Online Access: | https://www.mdpi.com/2075-4701/13/12/1958 |
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| author | Regina Buier Gabriella Stefania Szabó Gabriel Katona Norbert Muntean Liana Maria Muresan |
| author_facet | Regina Buier Gabriella Stefania Szabó Gabriel Katona Norbert Muntean Liana Maria Muresan |
| author_sort | Regina Buier |
| collection | DOAJ |
| description | The present work focuses on the investigation of protective coatings produced on zinc from chitosan (Chit) and an anionic dye, namely cresol red. Cresol red (CR) fulfills the basic requirements to be used as a corrosion inhibitor because it possesses a relatively high molecular weight and includes in its structure oxygen and sulfur atoms as well as aromatic rings. Moreover, it is an anionic compound that can interact with positively charged chitosan to produce reinforced coatings for zinc anti-corrosion protection. The influence of cresol red as a possible corrosion inhibitor for zinc substrates was investigated either in solution or incorporated in Chit coatings. Two preparation methods for the coatings were used: (i) Chit coating impregnation by immersion in the CR solution after Chit deposition on Zn, and (ii) chitosan mixing with the CR solution before applying the dip-coating technique. Potentiodynamic polarization curves were used to determine the kinetic parameters of the corrosion process. Long-term measurements were carried out in wet/dry cyclic conditions by using electrochemical impedance spectroscopy. EIS measurements recorded in 0.2 g/L Na<sub>2</sub>SO<sub>4</sub> at pH = 7 show an important increase in the impedance of the coatings occurring from the first until the fifty-fifth day in a row, in dry–wet cycles. This increase is due to the beneficial effect of CR incorporated in Chitosan and could be, at least partially, related to a consolidation of the Chit coating structure in the presence of CR by crosslinking between Chit and CR molecules. The structure of the coatings was studied, and the interactions between chitosan and cresol red were put into evidence by using FT-IR spectroscopy. Adhesion and wettability measurements were also carried out. The adhesion of Chit incorporating CR on Zn was better than that on glass substrates and reached ~99.99%, suggesting a better affinity of the chitosan coating towards the Zn substrate due to the existence of ZnO on the substrate surface. All the results show that CR could be used on zinc as a corrosion inhibitor incorporated in chitosan at basic pHs, but without taking advantage of its pH-indicating properties, which are lost due to the interactions occurring between the positively charged biopolymer and the negatively charged dye molecule. The preparation method of Chit coating impregnation with CR by immersion in the solution after deposition on Zn led to poorer results than the method in which chitosan was previously mixed with CR before applying the dip-coating technique. |
| first_indexed | 2024-03-08T20:32:40Z |
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| id | doaj.art-374c4e5a899440a0986a9c2b52f177ee |
| institution | Directory Open Access Journal |
| issn | 2075-4701 |
| language | English |
| last_indexed | 2024-03-08T20:32:40Z |
| publishDate | 2023-11-01 |
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| spelling | doaj.art-374c4e5a899440a0986a9c2b52f177ee2023-12-22T14:24:40ZengMDPI AGMetals2075-47012023-11-011312195810.3390/met13121958Influence of pH on the Inhibiting Characteristics of Cresol Red Incorporated in Chitosan Coatings on ZincRegina Buier0Gabriella Stefania Szabó1Gabriel Katona2Norbert Muntean3Liana Maria Muresan4Department of Chemical Engineering, “Babes-Bolyai” University Cluj-Napoca, 400028 Cluj-Napoca, RomaniaDepartment of Chemistry and Chemical Engineering Hungarian Line, “Babes-Bolyai” University Cluj-Napoca, 400028 Cluj-Napoca, RomaniaDepartment of Chemistry and Chemical Engineering Hungarian Line, “Babes-Bolyai” University Cluj-Napoca, 400028 Cluj-Napoca, RomaniaDepartment of Chemistry and Chemical Engineering Hungarian Line, “Babes-Bolyai” University Cluj-Napoca, 400028 Cluj-Napoca, RomaniaDepartment of Chemical Engineering, “Babes-Bolyai” University Cluj-Napoca, 400028 Cluj-Napoca, RomaniaThe present work focuses on the investigation of protective coatings produced on zinc from chitosan (Chit) and an anionic dye, namely cresol red. Cresol red (CR) fulfills the basic requirements to be used as a corrosion inhibitor because it possesses a relatively high molecular weight and includes in its structure oxygen and sulfur atoms as well as aromatic rings. Moreover, it is an anionic compound that can interact with positively charged chitosan to produce reinforced coatings for zinc anti-corrosion protection. The influence of cresol red as a possible corrosion inhibitor for zinc substrates was investigated either in solution or incorporated in Chit coatings. Two preparation methods for the coatings were used: (i) Chit coating impregnation by immersion in the CR solution after Chit deposition on Zn, and (ii) chitosan mixing with the CR solution before applying the dip-coating technique. Potentiodynamic polarization curves were used to determine the kinetic parameters of the corrosion process. Long-term measurements were carried out in wet/dry cyclic conditions by using electrochemical impedance spectroscopy. EIS measurements recorded in 0.2 g/L Na<sub>2</sub>SO<sub>4</sub> at pH = 7 show an important increase in the impedance of the coatings occurring from the first until the fifty-fifth day in a row, in dry–wet cycles. This increase is due to the beneficial effect of CR incorporated in Chitosan and could be, at least partially, related to a consolidation of the Chit coating structure in the presence of CR by crosslinking between Chit and CR molecules. The structure of the coatings was studied, and the interactions between chitosan and cresol red were put into evidence by using FT-IR spectroscopy. Adhesion and wettability measurements were also carried out. The adhesion of Chit incorporating CR on Zn was better than that on glass substrates and reached ~99.99%, suggesting a better affinity of the chitosan coating towards the Zn substrate due to the existence of ZnO on the substrate surface. All the results show that CR could be used on zinc as a corrosion inhibitor incorporated in chitosan at basic pHs, but without taking advantage of its pH-indicating properties, which are lost due to the interactions occurring between the positively charged biopolymer and the negatively charged dye molecule. The preparation method of Chit coating impregnation with CR by immersion in the solution after deposition on Zn led to poorer results than the method in which chitosan was previously mixed with CR before applying the dip-coating technique.https://www.mdpi.com/2075-4701/13/12/1958chitosancresol redelectrochemical methodspH effectzinc corrosion |
| spellingShingle | Regina Buier Gabriella Stefania Szabó Gabriel Katona Norbert Muntean Liana Maria Muresan Influence of pH on the Inhibiting Characteristics of Cresol Red Incorporated in Chitosan Coatings on Zinc Metals chitosan cresol red electrochemical methods pH effect zinc corrosion |
| title | Influence of pH on the Inhibiting Characteristics of Cresol Red Incorporated in Chitosan Coatings on Zinc |
| title_full | Influence of pH on the Inhibiting Characteristics of Cresol Red Incorporated in Chitosan Coatings on Zinc |
| title_fullStr | Influence of pH on the Inhibiting Characteristics of Cresol Red Incorporated in Chitosan Coatings on Zinc |
| title_full_unstemmed | Influence of pH on the Inhibiting Characteristics of Cresol Red Incorporated in Chitosan Coatings on Zinc |
| title_short | Influence of pH on the Inhibiting Characteristics of Cresol Red Incorporated in Chitosan Coatings on Zinc |
| title_sort | influence of ph on the inhibiting characteristics of cresol red incorporated in chitosan coatings on zinc |
| topic | chitosan cresol red electrochemical methods pH effect zinc corrosion |
| url | https://www.mdpi.com/2075-4701/13/12/1958 |
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