Effects of Immersion Time and 5-Phenyl-1H-tetrazole on the Corrosion and Corrosion Mitigation of Cobalt Free Maraging Steel in 0.5 M Sulfuric Acid Pickling Solutions

Table 2

EIS parameters obtained by fitting the Nyquist plots shown in Figures 5, 6, and 7 with the equivalent circuit shown in Figure 8 for the maraging steel in sulfuric acid solutions containing different concentrations of PHTA.

Solution	Parameter
	𝑅𝑆/Ω cm^2	𝑄		𝑅𝑃1/Ω cm^2	𝑅𝑃2/Ω cm^2	𝐿/𝐻
		𝑌𝑄/F cm^−2	𝑛
0.5 M H2SO4 (0 min)	1.46	0.01214	0.83	7.34	1.74	0.32
+1.0 mM PHTA (0 min)	1.65	0.00455	0.80	8.56	2.46	1.37
+5.0 mM PHTA (0 min)	1.94	0.00213	0.77	12.94	3.57	3.74
0.5 M H2SO4 (60 min)	1.33	0.04882	0.80	5.96	1.29	0.293
+1.0 mM PHTA (60 min)	1.48	0.00551	0.79	7.28	2.34	1.181
+5.0 mM PHTA (60 min)	1.78	0.00351	0.76	9.88	3.14	2.468
0.5 M H2SO4 (120 min)	1.05	0.06054	0.94	3.97	1.18	0.049
+1.0 mM PHTA (120 min)	1.24	0.01963	0.81	5.73	2.17	1.131
+5.0 mM PHTA (120 min)	1.49	0.01674	0.76	7.91	2.92	2.139