Synergistic Effect of Iodide Ion and 4-Hydroxy Coumarin on the Corrosion Inhibition of Mild Steel in Hydrochloric Acid

Table 3

Impedance parameters for corrosion of mild steel in 1 M HCl for different concentration of 4-hydroxy coumarin in the presence and absence of 10⁻³ M KI.

[Inh] M	[KI] M	𝑅ct  Ω cm^2	%IE	𝐶dl  μF/cm^2	%IE
Blank	—	15.65	—	425	—
—	10^−3	22.00	28.86	328	22.82
0.001	—	18.03	13.20	385	9.41
—	10^−3	23.04	32.07	344	19.06
0.003	—	19.71	20.60	376	11.53
—	10^−3	23.96	34.68	318	25.18
0.007	—	30.12	48.04	280	34.12
—	10^−3	41.94	62.68	124	70.82
0.009	—	31.44	50.22	278	34.59
—	10^−3	44.31	64.68	121	71.53
0.010	—	37.48	58.24	149	64.94
—	10^−3	51.58	69.60	111	73.88