Study on Steel Corrosion Rate in Semi Closed Seawater Area by Weight Loss Technique

Author(s): Hermine R. Z. Tadros1*, Mona F. El Naggar, Fatma A. Zaghloul, Aida B. Tadros1 & Gehan A. El Elaa

The influence of various environmental parameters on the corrosion rate of the metallic structures was studied. Different physicochemical and biological parameters were measured during the period June 2011 and May 2012 at Eastern harbor (EH), front of NIOF, Alexandria. Their ranges and (annual averages) were found as follows; temperature, 16.75- 29.73°C, (22.8°C); dissolved oxygen, 2.253-7.083ml/l, (4.089ml/l), pH 8.025 - 8.415. Total alkalinity recorded relatively high values, 2.838 -3.74meq/l, (3.35meq/l). The variations of the nutrient salts, PO4 -3 , NO2 -2 and NO-3 differed between, 0.588-5.5378μmol/l, (1.798μmol/l); 0.369-2.938μmol/l (1.658μmol/l) and 1.606- 15.633μmol/l (8.651μmol/l) respectively. Low level of SO4 2- was found, 1.933g/l-3.914g/l (2.954g/l). The phytoplankton annual average recorded 1.84x106 cells/l. The Bacillariophycea is dominating during most of the study year while the Dinophycea was frequent. The total annual average of bacterial count was 2271063 CFU/ml. The bacterial counts showed significant differences and their fluctuation in population distribution depends on the physicochemical variations. The corrosion of steel panel was measured for 24hrs twice a week monthly during the study period. The monthly corrosion rates fluctuated between 3.582 and 7.5518mpy with annual average 4.78303mpy (n=24). The change of steel rate of corrosion at the marine area is directly affected with sulphate concentration, and indirectly with temperature, pH and nitrite. The data also showed the decrease in steel corrosion accompanied by increase in viable counts of bacteria. The lower average corrosion rate measured during September (3.5819mpy) and November (3.783mpy) met with lower salinity. High corrosion rate during October, 6.0926mpy was affected by high DO level and the highest phytoplankton counts.


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