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

Table 1

%IE in presence of 10⁻³ M KI and synergism parameter.

[Inh]		10^−3 M KI	0.001	0.003	0.005	0.007	0.009	0.01
1 h	𝐼1,𝐼2	0.1778	0.0500	0.1537	0.2583	0.3718	0.4329	0.5586
	𝐼^′1+2	—	0.3472	0.4966	0.6200	0.6687	0.7122	0.7920
	𝑆	—	1.1970	1.3820	1.6650	1.5590	1.6200	1.7450
3 h	𝐼1,𝐼2	0.0915	0.0996	0.2727	0.3402	0.4373	0.4460	0.5678
	𝐼^′1+2	—	0.2610	0.4537	0.4959	0.5820	0.6474	0.7537
	𝑆	—	1.1070	1.2100	1.1890	1.2230	1.4270	1.5940
6 h	𝐼1,𝐼2	0.2799	0.2665	0.3949	0.4164	0.4897	0.5742	0.6252
	𝐼^′1+2	—	0.5339	0.5814	0.6189	0.6699	0.7307	0.7589
	𝑆	—	1.1330	1.0410	1.1030	1.1130	1.1390	1.1200
12 h	𝐼1,𝐼2	0.1139	0.1483	0.3011	0.3731	0.4592	0.4611	0.4759
	𝐼^′1+2	—	0.1907	0.3495	0.4346	0.4795	0.5619	0.6764
	𝑆	—	0.9330	0.9520	0.9830	0.9210	1.0900	1.4350