Inhibition of Corrosion of Carbon Steel in Well Water by DL-Phenylalanine-Zn²⁺ System

Table 4

Inhibition efficiencies and synergism parameters for various concentrations of DL-Phe-Zn²⁺ (5 ppm) system, when carbon steel is immersed in well water.

DL-phenylalanine ppm	Inhibition efficiency; IE (%)	Surface coverage θ 1	Zn^2+ ppm	Inhibition efficiency; IE (%)	Surface coverage θ 2	Combined IE % I′1+2	Combined surface coverage 𝜃^1+2	Synergism parameters 𝑆𝐼
50	41	0.41	5	15	0.15	65	0.65	1.4328
100	37	0.37	5	15	0.15	79	0.79	2.55
150	33	0.33	5	15	0.15	90	0.90	5.695
200	28	0.28	5	15	0.15	84	0.84	3.825
250	24	0.24	5	15	0.15	80	0.80	3.23

Immersion period: 7 days, pH = 8.