A Simple and Reliable Setup for Monitoring Corrosion Rate of Steel Rebars in Concrete

Table 2

Sample calculation for 𝑅_𝑝, 𝛽_𝑎, 𝛽_𝑐, and 𝐵.

Specimen ID: AC-4 with 𝐸corr=57 mV (CSE) and 𝑅=948 Ohm
𝐼	𝐸=𝑉	𝐸^′=𝑉−𝐼𝑅	𝜀=𝐸−𝐸corr	𝜀^′=𝐸^′−𝐸corr	𝑅𝑝 and 𝑅^′𝑝	Square of the error for (1) (without 𝐼𝑅 drop)	Square of the error for (1) (with 𝐼𝑅 drop)
(mA)	(mV)	(mV)	(mV)	(mV)	(Ohm)
0.0004	61.08	60.70	4.08	3.70	𝑅𝑝=6473; 𝑅^′𝑝=5525	11.530	11.534
0.0008	62.12	61.36	5.12	4.36		0.034	0.031
0.0012	63.65	62.51	6.65	5.51		7.138	7.047
0.0014	65.20	63.87	8.20	6.87		4.551	4.460
0.0017	67.10	65.48	10.10	8.48		5.288	5.160
0.0021	69.47	67.47	12.47	10.47		8.431	8.222
0.0023	71.62	69.43	14.62	12.43		1.076	1.007
0.0025	73.90	71.53	16.90	14.53		1.244	1.301
0.003	77.00	74.15	20.00	17.15		0.410	0.191
0.0035	80.50	77.18	23.50	20.18		1.135	1.128
Minimization of the sum of the squares of the error for best fitting (1) with the help of the Excel-Solver using constraints as follows: 𝛽𝑎 and 𝛽𝑐≥120 mV but ≤240 mV; 𝐵≥26 mV but ≤52 mV.						Min. sum = 40.836 at 𝛽𝑎=240 mV and 𝛽𝑐=193 mV; Therefore, from (2); 𝐵=46.57 mV	Min. sum = 40.085 at 𝛽𝑎=240 mV and 𝛽𝑐=187 mV; Therefore, from (2); 𝐵=45.69 mV