HIBISCO-COLIBRI EXTRACT AS GREEN CORROSION INHIBITOR FOR CARBON STEEL IN SULFURIC ACID

For this work, a hydroalcoholic extract was prepared from the aerial parts of the Malvaviscus arboreus (Malvaceae) species, popularly known as hibisco-colibri in Brazil; and then, investigated by infrared and NMR spectroscopy. A class of special metabolites containing a porphyrin skeleton and pyrrole units was determined by typical absorption spectra, mainly 1H and 13C NMR, thus indicating the capability of showing anti-corrosion effect. Therefore, the M. arboreus extract was examined as a corrosion inhibitor for AISI 1020 carbon steel in H2SO4 1 mol L-1, using a mass loss (gravimetric) technique. Results showed good corrosion inhibition efficiency, at both time and temperature variation. The maximum efficiency observed at 500 ppm was 97.5%, at 3 h, 24 h and 48 h. The surface morphology was analyzed by scanning electron microscopy (SEM), through which a higher homogeneity was observed in the presence of the M. arboreus extract. The hydroalcoholic extract of hibisco-colibri can be considered an efficient green agent for preventing corrosion.

本研究以巴西俗称蜂鸟木槿（hibisco-colibri）的锦葵科（Malvaceae）朱槿（Malvaviscus arboreus）的地上部分为原料，制备得到水醇提取物，并通过红外光谱与核磁共振波谱法对其开展表征分析。借助典型吸收光谱（主要为氢谱（¹H NMR）与碳谱（¹³C NMR）），鉴定出一类含有卟啉骨架与吡咯单元的特殊代谢产物，该类产物具备缓蚀性能。随后，本研究采用重量损失（重量法）技术，考察了该M. arboreus提取物作为缓蚀剂在1 mol·L⁻¹硫酸溶液中对AISI 1020碳钢的缓蚀效果。实验结果显示，在不同时间与温度条件下，该提取物均展现出良好的缓蚀效率；当提取物浓度为500 ppm时，于3 h、24 h及48 h下测得的最大缓蚀效率可达97.5%。通过扫描电子显微镜（SEM）对试样表面形貌进行分析，结果表明添加该提取物的体系表面均匀性显著提升。综上，蜂鸟木槿的水醇提取物可作为一种高效绿色缓蚀剂用于金属防腐。