Root and shoot extracts of Ajuga chamaecistus subsp. scoparia as natural inhibitors for 304 stainless steel corrosion in strong acidic medium

The inhibitive action of root and shoot extracts of Ajuga chamaecistus subsp. scoparia as a green inhibitors on corrosion of 304 stainless steel in the 6.0 M HCl solution was studied by the weight loss method, potentiodynamic polarization, electrochemical impedance spectroscopy, scanning electron microscopy, and atomic force microscopy. The results demonstrate that the extracts act as a show mixed-type inhibitor. The Nyquist plots display an increase of the charge transfer resistance with an increase of the inhibitor concentration and a decrease of the double layer capacitance. The effect of temperature and related activation parameters was deliberate. Adsorption of the extract followed the Langmuir isotherm model. The inhibition efficiencies found from electrochemical tests were in good agreement with those observed via the weight loss method. The inhibition efficiencies for root and shoot extracts are 99.4 and 99.6%, respectively.