Some Thiophene Derivatives as Corrosion Inhibitors for Carbon Steel in Hydrochloric Acid

Table 9

Corrosion potential (𝐸_corr), corrosion current density (𝑖_corr), Tafel slopes (𝛽_𝑐, 𝛽_𝑎), degree of surface coverage (𝜃), and inhibition efficiency (%IE_𝑝) of carbon steel in 1 M HCl at 25°C for compounds A, B, and C.

Inhibitor	Concentration; × 10^−5 (M)	−𝐸corr. (mV)	𝑖corr. (μA cm^−2)	𝛽𝑐 (mV dec^−1)	𝛽𝑎 (mV dec^−1)	𝑘corr. (mpy)	𝜃	%IE𝑝
1 M HCl	Blank	511	2170	206.7	205.3	992.3	—	—
A	2	449	695	199	111	317.6	0.680	68.0
	4	447	543	195	118	248.1	0.750	75.0
	6	438	458	183	99	209.1	0.789	78.9
	8	447	409	168	85	186.9	0.812	81.2
	10	422	278	157	79	127.0	0.872	87.2
	12	436	181	145	79	82.8	0.917	91.7
B	2	507	1900	257	182	866.8	0.124	12.4
	4	504	1130	188	136	516.3	0.479	47.9
	6	497	800	189	154	365.6	0.631	63.1
	8	486	453	188	133	207.1	0.791	79.1
	10	482	310	140	105	141.5	0.857	85.7
	12	472	205	162	108	93.9	0.906	90.6
C	2	522	2050	211	188	936.6	0.055	5.5
	4	526	1780	165	122	815.3	0.180	18.0
	6	516	1200	167	125	549.2	0.447	44.7
	8	474	455	171	119	196.9	0.790	79.0
	10	491	387	130	85	176.8	0.822	82.2
	12	478	310	140	97	141.7	0.857	85.7