Research Article

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 growthDMaximum overall pit growthAverageE system (versus Ag-AgCl)AvgerageE chlorine demand
 Adjustment to control water 95% CI mV95% CImg/week/cm295% CI

None
 ControlS186383.40.28.6549119.10.2
Control L12102072.20.23.8458343.20.4

Free chlorine (mg/L as Cl2)
 0.5S21240.00.00.112781.60.1
 1S31240.00.00.1140101.60.0
 2S42202120.70.21.5223243.10.1
 3S588821.90.44.0380566.10.1
 8S688342.60.59.66252810.10.3
0.4L24900.30.00.5179140.10.0

Orthophosphate (mg/L as P)
 0.015S788482.50.46.8488704.70.1
 0.025S888542.50.46.1316404.30.2
 0.1S9880.10.10.014272.30.1
 0.25S10880.10.10.011762.80.2
 0.5S11880.00.00.012152.20.1
 1S12880.10.10.011741.80.1
0.1L34903571.40.12.2301442.30.6
1L44900.10.00.28850.30.2

Silica (mg/L as Si)
 0.1S1386433.10.37.6637119.30.1
 0.5S1486342.10.59.663495.00.1
 2.5S15860.10.00.211565.10.1
 10S16860.10.00.311342.70.1
0.5L54903570.90.12.2356312.20.3
5L64900.20.00.3139160.30.2

Organic matter (mg/L as TOC)
 0.005AS1786462.30.59.1574126.90.1
 0.01AS1886382.60.36.8521186.40.2
 0.05AS19860.80.11.422063.80.1
 0.05BS20861.30.22.1276104.80.1
 0.05CS2186533.50.36.2471117.10.1
L72101931.90.24.1366342.30.3
L84904551.10.11.7245130.40.2

Alkalinity (mg/L as CaCO3)
 10L91891722.60.24.6511376.01.1
 150L104900.50.00.7593730.70.3

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).