Fitting results using model I and model II for impedance spectra recorded after 48 h exposure in deaerated 0.05 mol dm⁻³ NaCl solution of titanium samples without anodizing in DES bath^a.

Sample	Model	R s (Ω cm2)	CPE-T (Ω−1 cm−2 s−P)	CPE-P	R (Ω cm2)	W s			Goodness of fit (χ2)
						W s-R	W s-T	W s-P
As-delivered	Model I	82	1.80 × 10−5	0.926	1.03 × 107	n.a.	n.a.	n.a.	1.9 × 10−4
	Model II	82	1.73 × 10−5	0.935	9.16 × 105	1.12 × 107	51.9	0.67	6.5 × 10−6
Etched	Model I	64	2.65 × 10−5	0.944	3.25 × 106	n.a.	n.a.	n.a.	6.2 × 10−4
	Model II	64	2.46 × 10−5	0.960	2.08 × 105	4.32 × 106	63.9	0.61	9.4 × 10−5

^an.a. – not applicable in model I.