Table 3. Impedance parameters of mild steel in 0.5 M HCl solution in the presence and absence of DAP, TTA and combination of them at 298 K.

C (mM)	Rs (Ω cm2)	Rct (Ω cm2)	SD	Y0 × 10−6 (S sn cm−2)	n	Cdl (μF cm−2)	η (%)
Blank	2.03	26.97	0.31	267.3	0.83	98.2	/
DAP
1	1.71	59.30	0.36	256.0	0.80	96.6	54.5
2	1.58	69.66	0.25	237.2	0.81	94.8	61.3
4	1.80	114.8	0.48	233.2	0.80	91.3	76.5
10	1.62	167.9	0.41	216.5	0.79	90.3	83.9
TTA
0.5	1.60	86.65	0.39	246.8	0.82	98.1	68.9
1	0.91	93.06	0.63	403.6	0.70	94.2	71.0
2	1.97	93.27	0.61	266.6	0.80	94.7	71.1
5	1.42	108.2	0.97	223.0	0.81	91.4	75.0
Synergy
Num-1	0.83	130.5	1.14	210.8	0.83	90.9	79.3
Num-2	0.92	198.5	1.67	165.0	0.82	80.1	86.4
Num-3	1.02	292.7	1.46	157.4	0.82	78.3	90.8
Num-4	0.82	337.4	1.52	128.8	0.83	68.0	92.0