<p>Carbon quantum dots (CQDs) are more effective than traditional corrosion inhibitors due to their environmentally friendly nature and strong corrosion resistance. Utilizing waste biodegradable plastic bags, which are rich in carbon sources, to produce CQDs offers a sustainable solution for addressing the corrosion of Mg alloys. In this study, nitrogen- and sulfur-doped carbon quantum dots (N/S(CDs)) were synthesized using a hydrothermal method, and their corrosion inhibition performance on Mg alloy AZ31 in a 3.5 wt% NaCl solution was evaluated. Structural characterization via TEM, FTIR, and UV–Vis confirmed that the N/S(CDs) possessed graphitic carbon structures with N- and S-functionalized. Electrochemical tests revealed that the corrosion inhibition efficiency was concentration-dependent, with the highest performance observed at 200 mg/L N/S(CDs), where the inhibition rate reached approximately 81%. This was attributed to the formation of a protective layer on the alloy surface. After soaking in a 200 mg/L N/S(CDs) NaCl solution for 5 h, the film gradually degraded due to dissolution reactions, and the inhibition efficiency decreased to 26%. Langmuir adsorption studies revealed that N/S(CDs) adhered to the alloy surface through both chemical and physical adsorption mechanisms, with a <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10853_2025_11749_Article_IEq1.gif" Format="GIF" Height="21" Rendition="HTML" Resolution="72" Type="Linedraw" Width="45" /> </InlineMediaObject> <EquationSource Format="TEX">$\Delta G_{{{\text{ads}}}}^{{0}}$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi mathvariant="normal">Δ</mi> <msubsup> <mi>G</mi> <mrow> <mtext>ads</mtext> </mrow> <mn>0</mn> </msubsup> </mrow> </math></EquationSource> </InlineEquation> value of − 27.55 kJ/mol. Surface characterization by SEM, AFM, and XPS confirmed the formation of a protective N/S(CDs) layer, effectively preventing the infiltration of corrosive ions. This study highlights the potential of N/S(CDs) as a sustainable corrosion inhibitor for Mg alloys.</p> Graphical abstract <p></p>

Insights into the anticorrosion mechanism of carbon quantum dots as green inhibitors for AZ31 Mg alloy in 3.5 wt% NaCl solution

期刊论文
发表日期：

2025年11月5日

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Wenting Zhao,
Rui Wan,
Bo Liu,
Zhenqiang Wang,
Zhili Gong,
Lei Guo,
Riadh Marzouki,
Xin Li,
Wenpo Li,
Jianchun Sun,
Bochuan Tan,
Yiling Fang,
Qingwei Dai

摘要

Carbon quantum dots (CQDs) are more effective than traditional corrosion inhibitors due to their environmentally friendly nature and strong corrosion resistance. Utilizing waste biodegradable plastic bags, which are rich in carbon sources, to produce CQDs offers a sustainable solution for addressing the corrosion of Mg alloys. In this study, nitrogen- and sulfur-doped carbon quantum dots (N/S(CDs)) were synthesized using a hydrothermal method, and their corrosion inhibition performance on Mg alloy AZ31 in a 3.5 wt% NaCl solution was evaluated. Structural characterization via TEM, FTIR, and UV–Vis confirmed that the N/S(CDs) possessed graphitic carbon structures with N- and S-functionalized. Electrochemical tests revealed that the corrosion inhibition efficiency was concentration-dependent, with the highest performance observed at 200 mg/L N/S(CDs), where the inhibition rate reached approximately 81%. This was attributed to the formation of a protective layer on the alloy surface. After soaking in a 200 mg/L N/S(CDs) NaCl solution for 5 h, the film gradually degraded due to dissolution reactions, and the inhibition efficiency decreased to 26%. Langmuir adsorption studies revealed that N/S(CDs) adhered to the alloy surface through both chemical and physical adsorption mechanisms, with a $\Delta G_{{{\text{ads}}}}^{{0}}$ $Δ G_{ads}^{0}$ value of − 27.55 kJ/mol. Surface characterization by SEM, AFM, and XPS confirmed the formation of a protective N/S(CDs) layer, effectively preventing the infiltration of corrosive ions. This study highlights the potential of N/S(CDs) as a sustainable corrosion inhibitor for Mg alloys.

Graphical abstract