Corrosion Inhibition of Mild Steel in Acidic Media by 5′-Phenyl-2′,4′-dihydrospiro[indole-3,3′-pyrazol]-2(1H)-one

Table 6

Impedance parameters for the corrosion of mild steel in 1 M HCl and 0.5 M H₂SO₄ with and without inhibitor.

Name of the inhibitor	Inhibitor concentration (ppm)	1 M HCl			0.5 M H2SO4
		𝑅ct (ohms)	𝐶dl; (farads) × 10^−5	Inhibition efficiency (%)	𝑅ct (ohms)	𝐶dl; (farads) × 10^−5	Inhibition efficiency (%)
	Blank	136.53	1.1717		11.32	6.2030
	1	154.83	2.1938	11.8	37.49	2.8020	69.8
SPAH	5	168.33	2.7641	18.9	55.50	2.3966	79.6
	9	227.45	1.6896	40.0	60.94	2.4798	81.4