Report No DWI0097

GALVANIC CORROSION OF LEAD IN COPPER PIPEWORK: PHASE I, MEASUREMENT OF GALVANIC CORROSION POTENTIALS IN SELECTED WATERS 392-S

DWI0097

Oct 1985

SUMMARY

OBJECT

The objective of the work reported was to survey selected water supplies, in collaboration with water undertakings, to assess the level of galvanic corrosion of lead solder coupled to copper using voltage measurements from corrosion cells. This report presents the work done during the period December 1983 to November 1984.

APPROACH

The galvanic corrosion potential of thirty-eight different waters were measured using corrosion cells. The waters were selected to represent typical extremes of water quality parameters previously established to have significant effects on the galvanic corrosion.

RESULTS

A wide range in corrosion potential, greater than 85:1, was found. The value of corrosion potential was dependent on water quality. Multiple regression analysis established the most significant effects on voltage are associated with the chloride to sulphate concentration ratio and the chloride and nitrate concentrations. For data sub-groups significant effects are associated also with alkalinity, sulphate and silicate concentrations. No significant effect is associated with pH.

Strong intercorrelations were found between water quality parameters which accounts for the significant effect on voltage associated with alkalinity.

The extent to which variance was accounted for in the multiple regression analyses was poor and dependent on the data group. This suggests that other water quality parameters not measured in this work, may also significantly affect corrosion potential. Three waters produced voltages significantly greater than the other waters and some reasons for these are given. Eight waters produced voltages lower than the general distribution in voltages. The distinctive water quality features of this sub-group have not been identified.

CONCLUSIONS

The results generally substantiate the conclusions of previous work by WRc. Dosing to increase sulphate or silicate concentrations might reduce corrosion potential. Further work should be done to test these and other treatments for reducing corrosion potentials.

Copies of this report may be available as an Acrobat pdf download under the 'Pre 2000 Reports' heading on the DWI website.