EIS parameters for the corrosion of mild steel in 20% formic acid in the presence and absence of different concentrations of 8b and 2 mmol KI at 30 °C.

Conc. (ppm)	KI (mmol)	L (H cm2)	R L (Ω cm2)	R ct (Ω cm2)	n	C dl (μF cm−2)	Z w × 10−3 (Ω cm2)	η (%)
Blank	—	45.17	21.82	45.13	0.917	50.78	—	—
1	—	12.98	19.53	97.99	0.782	41.90	—	53.9
1	2	—	—	845.9	0.844	21.85	179.1	94.7
5	—	24.21	31.33	111.4	0.847	39.00	—	59.5
5	2	—	—	994.1	0.769	23.87	10.07	95.5
10	—	19.96	36.95	139.1	0.801	39.56	—	67.6
10	2	—	—	1015	0.756	22.96	8.772	95.6
20	—	29.16	36.59	154.9	0.839	37.70	—	70.9
20	2	—	—	1159	0.799	20.83	11.18	96.1
50	—	42.43	43.05	175.9	0.830	37.40	—	74.3
50	2	—	—	1381	0.760	42.21	8.038	96.7
100	—	38.71	47.15	192.1	0.785	42.06	—	76.5
100	2	—	—	1460	0.800	26.71	8.327	96.9