Abstract:
Water pipe surface deterioration is the result of continuous electrochemical reactions
attacking the surface due to the interaction of the pipe surface with environments through the time
function. The study presents corrosion characterization at the surface and sub-surface of damaged
ductile iron pipe (DIP) and galvanized steel (GS) pipes which served for more than 40 and 20 years,
respectively. The samples were obtained from Addis Ababa city water distribution system for the
analysis of corrosion morphology patterns at different surface layers. Mountains 8.2 surface analysis
software was utilized based on the ISO 25178-2 watershed segmentation method to investigate
corrosion features of damaged pipe surface and to evaluate maximum pit depth, area, and volume
in-situ condition. Based on the analysis maximum values of pit depth, area and volume were
380 µm, 4000 µm2
, and 200,000 µm3
, respectively, after 25% loss of the original 8 mm thickness
of DIP. Similarly, the pit depth of the GS pipe was 390 µm whereas the maximum pit area and
volume are 4000 µm2 and 16,000 µm3
, respectively. In addition, characterizations of new pipes were
evaluated to study microstructures by using an optical microscope (OM), and a scanning electron
microscope (SEM) was used to analyze corrosion morphologies. Based on the SEM analysis, cracks
were observed at the sub-surface layer of the pipes. The results show that uniform corrosion attacked
the external pipe surface whereas pitting corrosion damaged the subsurface of pipes. The output of
this study will be utilized by water suppliers and industries to investigate corrosion phenomena at
any damage stage.
