Natural corrosion inhibition of stainless steel in phosphoric medium by betacyanin and betaxanthin pigments extracted from moroccan prickly pear juices

Author(s): Hasna El Gharras, Khadija Hnini, Abdelilah Chtaini, Aziz Hasib, Abderrahim Jaouad

The inhibitive action of natural pigments (Red andYellow) extracted from prickly pear fruits (Opuntia ficus-indica) towards corrosion of stainless steel in phosphoric acid was investigated using, electrochemical polarisation and electrochemical impedance spectroscopy (EIS) methods. It was found that the presence of natural pigments reduce the corrosion rate of the testedmetal especially in addition of the red pigments (97%). The inhibition efficiency increases as the pigment concentration of extracts increased. It was also found that the pigments tested act as mixed inhibitors. The inhibitive action of the extracts is discussed in term of adsorption and that such adsorption follows Langmuir adsorption isotherm. The calculated values of the free energy of adsorption indicated that the adsorption process is spontaneous.

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