Impedance parameters and inhibition efficiency of mild steel in 1 M HCl in the absence and presence of studied inhibitors after 1 h immersion.

C (mM)	R s (Ω cm2)	CPE (μF cm−2)	n	R p (Ω cm2)	η
Blank	1.20	664	0.82	8.77	—
l -Histidine
0.5	1.16	523	0.83	10.88	19.4
1	1.43	432	0.85	12.88	31.9
2	1.24	328	0.83	17.01	48.4
LHIL
0.5	1.21	310	0.87	12.28	28.6
1	1.06	73.6	0.83	233	96.2
2	1.34	58.3	0.81	755	98.8