Inhibition of Copper Pitting Corrosion in Aggressive Potable Waters
Table 3
Summary of experimental results. Tests are grouped by respective adjustments to control water quality and large-scale results are bolded. The large-scale control, 1 mg/L phosphate and 5 mg/L Si test data has been partially published elsewhere in a different context [5], and is included here for completeness and comparison.
Test
Number
Duration days
Failure time days
Average overall pit growthD
Maximum overall pit growth
AverageE system (versus Ag-AgCl)
AvgerageE chlorine demand
Adjustment to control water
95% CI
mV
95% CI
mg/week/cm2
95% CI
None
Control
S1
86
38
3.4
0.2
8.6
549
11
9.1
0.2
Control
L1
210
207
2.2
0.2
3.8
458
34
3.2
0.4
Free chlorine (mg/L as Cl2)
0.5
S2
124
—
0.0
0.0
0.1
127
8
1.6
0.1
1
S3
124
—
0.0
0.0
0.1
140
10
1.6
0.0
2
S4
220
212
0.7
0.2
1.5
223
24
3.1
0.1
3
S5
88
82
1.9
0.4
4.0
380
56
6.1
0.1
8
S6
88
34
2.6
0.5
9.6
625
28
10.1
0.3
0.4
L2
490
—
0.3
0.0
0.5
179
14
0.1
0.0
Orthophosphate (mg/L as P)
0.015
S7
88
48
2.5
0.4
6.8
488
70
4.7
0.1
0.025
S8
88
54
2.5
0.4
6.1
316
40
4.3
0.2
0.1
S9
88
—
0.1
0.1
0.0
142
7
2.3
0.1
0.25
S10
88
—
0.1
0.1
0.0
117
6
2.8
0.2
0.5
S11
88
—
0.0
0.0
0.0
121
5
2.2
0.1
1
S12
88
—
0.1
0.1
0.0
117
4
1.8
0.1
0.1
L3
490
357
1.4
0.1
2.2
301
44
2.3
0.6
1
L4
490
—
0.1
0.0
0.2
88
5
0.3
0.2
Silica (mg/L as Si)
0.1
S13
86
43
3.1
0.3
7.6
637
11
9.3
0.1
0.5
S14
86
34
2.1
0.5
9.6
634
9
5.0
0.1
2.5
S15
86
—
0.1
0.0
0.2
115
6
5.1
0.1
10
S16
86
—
0.1
0.0
0.3
113
4
2.7
0.1
0.5
L5
490
357
0.9
0.1
2.2
356
31
2.2
0.3
5
L6
490
—
0.2
0.0
0.3
139
16
0.3
0.2
Organic matter (mg/L as TOC)
0.005A
S17
86
46
2.3
0.5
9.1
574
12
6.9
0.1
0.01A
S18
86
38
2.6
0.3
6.8
521
18
6.4
0.2
0.05A
S19
86
—
0.8
0.1
1.4
220
6
3.8
0.1
0.05B
S20
86
—
1.3
0.2
2.1
276
10
4.8
0.1
0.05C
S21
86
53
3.5
0.3
6.2
471
11
7.1
0.1
L7
210
193
1.9
0.2
4.1
366
34
2.3
0.3
L8
490
455
1.1
0.1
1.7
245
13
0.4
0.2
Alkalinity (mg/L as CaCO3)
10
L9
189
172
2.6
0.2
4.6
511
37
6.0
1.1
150
L10
490
—
0.5
0.0
0.7
593
73
0.7
0.3
S indicates small-scale pipe loop and L indicates large-scale pipe-loop.
ANOM, Bozonated NOM and Csodium acetate/d-glucose.
DAverage pit growth rates computed from 24 (small-scale tests) or 48 (large-scale) deepest pits measured on copper surfaces contacted by flow.
EAverage of measurements from week 3 (small-scale tests) or for weeks 5–22 (large-scale).