The inhibitive action of Foeniculum vulgare seeds (FVS) hydracid extract on C38 steel corrosion in 1M HCl solution was investigated by gravimetric and Tafel polarization curves techniques. The results show FVS to be a good inhibitor in acid solution. Inhibition efficiency (IE) increased with concentration and decreased with temperature for FV extract in HCl solution. The polarization curve of Tafel revealed that the FVS hydracid extract acts as a
mixed-type inhibitor. The mechanism of adsorption proposed for FVS hydracid extract is physisorption in HCl solution and the adsorption obeys Langmuir isotherm.