Electrochemical and Thermodynamic Investigation on Corrosion Inhibition of C38 Steel in 1M Hydrochloric Acid Using the Hydro-Alcoholic Extract of Used Coffee Grounds

Table 3

Slopes of the Bode plots at intermediate frequencies, the maximum phase angles (θ_max) and the corresponding frequencies (freq_max) for C38 steel in 1 M HCl solution containing different concentrations of HECG at different temperatures.

Temperature (K)	C (g/L)	θ max (deg)	freq max	Slope
293.15	Blank	48.10	2.09	−0.52
	0.25	65.09	2.60	−0.75
	0.5	65.60	2.26	−0.74
	1.0	65.90	2.60	−0.74
	1.5	66.59	2.60	−0.72
	2	69.34	3.12	−0.70
303.15	Blank	46.69	0.32	−2.94
	0.25	60.83	0.38	−3.64
	0.5	61.76	0.416	−3.72
	1.0	62.17	0.38	−3.86
	1.5	63.44	0.416	−3.68
	2	64.67	0.47	−3.18
313.15	Blank	37.19	0.35	−2.29
	0.25	58.18	0.41	−3.83
	0.5	58.38	0.41	−3.85
	1.0	60.27	0.41	−3.93
	1.5	62.69	0.41	−4.13
	2	63.16	0.49	−3.48
323.15	Blank	35.09	2.43	−0.32
	0.25	55.56	2.60	−0.54
	0.5	56.78	2.60	−0.54
	1.0	56.94	2.60	−0.53
	1.5	58.10	2.60	−0.57
	2	59.09	3.46	−0.43