Table 3. Impedance Parameters for Corrosion of Mild Steel (XC70) in (HCl, 1 M DMSO) without and with Different Concentrations of the Inhibitors (C1, C2, and C3) at 25 °C.

compounds	Cinh (M)	Rct (Ω cm2)	Cdl (μF/cm2)	n	IE (%)	θ
C1	blank	73	153.5	0.8772
	1 × 10–6	103.3	61.77	0.7281	29.33	0.2933
	2 × 10–6	111.4	65.29	0.7591	34.47	0.3447
	1 × 10–5	147.8	70.79	0.7761	50.60	0.5060
	6 × 10–5	186.7	54.14	0.7884	61.78	0.6178
	SD	43.83	40.92	0.055	23.55	0.24
	Pearson χ2	0.93	–0.76	1.00	0.87	0.87
C2	blank	73	153.5	0.8762
	1 × 10–6	97.98	57.88	0.7781	48.32	0.4832
	2 × 10–6	185.1	67.16	0.7876	60.5	0.605
	1 × 10–5	195	81.54	0.7894	62.56	0.6256
	6 × 10–5	371.4	84.03	0.7937	80.18	0.8018
	SD	117.22	37.70	0.040	30.34	0.30
	Pearson χ2	0.95	0.72	1.00	0.92	0.92
C3	blank	73	153.5	0.8736
	1 × 10–6	97.98	66.66	0.7491	25.49	0.2549
	2 × 10–6	138.8	101.9	0.7631	47.40	0.4740
	1 × 10–5	151	86.46	0.7781	51.56	0.5156
	6 × 10–5	154.4	42.03	0.7957	52.72	0.5272
	SD	35.87	41.93	0.048	22.67	0.23
	Pearson χ2	0.57	–0.81	1.00	0.53	0.53