As a result of in-service external corrosion, a steel water pipeline was suffering from loss of wall thickness, with leaks in some areas. A cost effective repair method was required, as the water company did not wish to replace the pipeline.
• cut out grossly corroded sections, replace with patches or new pipe lengths, and repair by welding on site (expensive, long installation downtime);
• use adhesive bonding to repair cavities and holes in the pipeline.
What Was Done
Two types of adhesive bonding approach were considered:
• to fill up the cavities and restore the external surface;
• to repair holes of up to 5 mm in diameter.
The procedure adopted was to degrease the damaged surfaces using a trichloroethene product, abrade, and then fill with a mastic compound such as Araldite 64257, hardener HY 850 and silica filler. A similar approach was used to rebuild the external coating, except that the epoxy was reinforced with layers of glass fibre chopped strand mat.
Both the corroded area and a steel patch (200 x 200 x 2 mm) were cleaned and degreased. Priming and anticorrosion treatment was applied and a patch bonded in place using epoxy adhesive. The patches were held in position by a series of metal straps until the cure was complete.
Satisfactory pipeline performance was obtained by use of the above adhesive repair method. Complete replacement of the pipeline was avoided.
Provided resistance to humidity is achieved, the use of adhesive repairs is attractive for this type of application.