Supplementary material:

The effect of non ionic surfactants containing triazole, thiadiazole and oxadiazole as inhibitors for the corrosion of carbon steel in 1M hydrochloric acid

Mohamed Sobhi Ma,*, Refaat El-Sayedb, MetwallyAbdallahMa,b

a Department of Chemistry, Faculty of Science, Benha University, Benha, Qalubya, Egypt

*E-mail address:

bDepartment of Chemistry, Faculty of Science, Umm Al-Quura University, Makkah Al-Mukarramah, Saudi Arabia

(I)Yield 65 %; IR: (cm-1)  = 3410-3200 (NH, NH2), 1541 (C=N), 1275 (C=S). 1H NMR (CDCl3): δ = 0.96 (t, 3H, Me), 1.29-1.36 (m, 28H, 14CH2), 5.62 (s, 1H, NH), 9.5 (s, 2H, NH2). 13C NMR (CDCl3): δ = 165 (thioamide), 155 (imine), (32.1, 29.6, 29.3, 25.5, 22.5, 21.7, 14.2) aliphatic chain. Anal. Calcd for C17H34N4S (326.54): C, 62.53; H, 10.49; N, 17.16; S, 9.82 %. Found C, 62.62; H, 10.61; N, 17.10; S, 10.01 %.

(II)Yield 65 %; IR: (cm-1)  = 3260-3200 (NH), 1499 (C=N), 1250 (C=S). 1H NMR (CDCl3): δ = 0.95 (t, 3H, Me), 1.29-1.33 (m, 28H, 14CH2), 7.27, 9.44 (s, 2H, 2NH).13C NMR (CDCl3): δ = 188 (thioamide), 155 (imine), (31.8, 30.6, 29.5, 22.1, 21.7, 14.1) aliphatic chain. Anal. Calcd for C17H33N3S (311.53): C, 65.54; H, 10.68; N, 13.49; S, 10.29 %. Found C, 65.71; H, 10.75; N, 13.66; S, 10.41 %.

(III)Yield 75 %; IR: (cm-1)  = 3260 (NH), 1549 (C=N), 1460 (C=S). 1H NMR (CDCl3): δ = 0.86 (t, 3H, Me), 1.29-1.36 (m, 28H, 14CH2), 7.27 (s, 1H, NH). Anal. Calcd for C17H32N2S2 (328.58): C, 62.14; H, 9.82; N, 8.53; S, 19.52 %. Found C, 62.33; H, 10.01; N, 8.74; S, 19.65 %.

(IV)Yield 79 %; IR: (cm-1)  = 3210 (NH), 1559 (C=N), 1260 (C=S). 1H NMR (CDCl3): δ = 0.95 (t, 3H, Me), 1.22-1.35 (m, 28H, 14CH2), 7.27 (s, 1H, NH). Anal. Calcd for C17H32N2OS (312.51): C, 65.34; H, 10.32; N, 8.96; S, 10.26 %. Found C, 65.44; H, 10.52; N, 9.11; S, 10.20 %.

Fig. 1

Fig. 2

Fig. 3

Fig. 4

Fig. 5

Fig. 6

Fig. 7 Plot of ln (CR/T) vs. 1000/T for carbon steel in 1MHCl solution in the absence and presence of inhibitors (I): (1) 0.00M (2) 5x10-6 M (3) 1x10-5(4) 5x10-5 M (5) 1x10-4 M (6) 5x10-4M.

Fig. 8 Plot of ln (CR/T) vs. 1000/T for carbon steel in 1MHCl solution in the absence and presence of inhibitors (II): (1) 0.00M (2) 5x10-6 M (3) 1x10-5(4) 5x10-5 M (5) 1x10-4 M (6) 5x10-4M.

Fig. 9 Plot of ln (CR/T) vs. 1000/T for carbon steel in 1MHCl solution in the absence and presence of inhibitors (III): (1) 0.00M (2) 5x10-6 M (3) 1x10-5(4) 5x10-5 M (5) 1x10-4 M (6) 5x10-4M.

Fig. 10 Plot of ln (CR/T) vs. 1000/T for carbon steel in 1MHCl solution in the absence and presence of inhibitors (IV): (1) 0.00M (2) 5x10-6 M (3) 1x10-5(4) 5x10-5 M (5) 1x10-4 M (6) 5x10-4M.

Inhibitor
system / Temperature (K) / Kadsx103 / ΔGoads(kJ mol-1) / ΔHoads(kJ mol-1) / ΔSoads(kJ mol-1)
Compd. I / 303 / 48.00 / -36.50 / -28.23 / -27.26
313 / 31.33 / -36.60 / -26.74
323 / 20.23 / -36.62 / -26.01
333 / 14.67 / -36.90 / -26.00
Compd. II / 303 / 38.00 / -35.91 / -26.55 / -30.90
313 / 26.58 / -36.19 / -30.79
323 / 20.22 / -36.62 / -31.19
333 / 16.19 / -37.16 / -31.85
Compd. III / 303 / 31.34 / -35.43 / -25.70 / -32.14
313 / 23 / -35.82 / -32.33
323 / 16.18 / -36.04 / -32.81
333 / 13.40 / -36.64 / -32.85
Compd. IV / 303 / 20.23 / -34.35 / -24.95 / -30.05
313 / 13.40 / -34.44 / -30.32
323 / 11.40 / -35.10 / -31.43
333 / 9.80 / -35.80 / -32.54

Table 1 Thermodynamic parameters of adsorption for carbon steel in 1MHCl solution obtained from weight loss measurements.

Table 2

Activation parameters for the dissolution of carbon steel in 1MHCl solution in absence and presence of inhibitors.

Inhibitor
system / Concentration (M) / Ea (kJ mol-1) / ΔH* (kJ mol-1) / -ΔS* (JK-1 mol-1)
Blank / ------ / 50.7 / 48.1 / 70.8
5x10-6 / 51.5 / 48.8 / 62.7
1x10-5 / 55.5 / 53.1 / 53.4
Compd. I / 5x10-5 / 69.2 / 66.5 / 49.7
1x10-4 / 81.8 / 79.3 / 36.2
5x10-4 / 50.7 / 48.1 / 70.8
5x10-6 / 50 / 47.6 / 68.3
1x10-5 / 50.7 / 48.2 / 60.9
Compd. II / 5x10-5 / 52.5 / 50 / 53.5
1x10-4 / 61.8 / 59.4 / 44.8
5x10-4 / 68.7 / 66.2 / 37.8
5x10-6 / 49.7 / 47.2 / 69.5
1x10-5 / 50.8 / 48.2 / 62
Compd. III / 5x10-5 / 51.3 / 49.4 / 57.2
1x10-4 / 52.8 / 50.4 / 43.2
5x10-4 / 67.8 / 65.1 / 35.7
5x10-6 / 51.4 / 48.7 / 66.9
1x10-5 / 52.2 / 49.6 / 59
Compd. IV / 5x10-5 / 55.6 / 52.8 / 50.1
1x10-4 / 58.2 / 55.6 / 46.2
5x10-4 / 63.5 / 61 / 34.5