Table 3. Tafel Polarization Parameters and Corrosion Inhibition Efficiencies for Aluminum in a 4 M NaOH Solution in the Presence and Absence of Lignin Molecules.

concentration (ppm)	–Ecorr (V)	βa (mV dec–1)	–βc (−mV dec–1)	icorr (mA cm–2)	ηe (%)
0	1.63	1.670	0.854	41.52
100	1.67	2.666	0.967	37.53	9.6
500	1.74	2.425	1.003	33.92	18.3
600	1.74	2.063	0.930	31.89	23.2
800	1.78	2.020	0.864	27.48	33.8
1000	1.76	1.690	0.828	25.84	37.8
1500	1.80	1.431	0.775	21.17	49.0