ST37 STEEL CORROSION RISK POTENTIAL IN CIRATA RESERVOIR BY ANAEROBIC BACTERIA

• Main Author: Hasuri, Hanifah
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/49505
• Institution: Institut Teknologi Bandung

Water quality decreased when uncontrolled fishery activity was taking place in the water body which potentially causing harm and intensifying corrosion risk around the dam infrastructure. Study was conducted in order to determine anaerobic bacteria prominent role in escalating steel ST37 corrosion on both field and laboratory scale and to discover corrosion risk potential on different water depth of Cirata Reservoir. Water from 0,5 m (F0.5) and 10 m (F10) below surface was directly monitored on field every 3 months in one-year cycle. Corrosion rate test in anaerob laboratory condition was carried out using inoculum from same water dam (L0.5 and L10) for 56 days long. Physicochemical (DO, conductivity, pH, temperature, NO3 -, HS-), corrosion rate, corrosion behavior (visualization by stereo microscope, SEM-EDS) and microbiological analysis (16s rRNA, dsrA, bacterial community) were obtained from the study. Sample (F0.5 and F10) results originated from dry season (August 2019) to rainy season (February 2020) shown different corrosion behavior in biofilm and corrosion product forms. Oxidation process fostered production of red-brown colored corrosion product in F0.5 sample, whilst F10 had black colored corrosion product from iron and bacterial metabolites interaction in water body. The resulting differences were influenced by variation of DO (F0.5 5.67 mg/mL and F102.53 mg/mL), BOD (F0.5 10.16 mg/mL and F10 14.44 mg/mL), TOC (F0.5 5.31 mg/mL and F10 7.52 mg/mL), pH (F0.5 7.8 and F10 6.85), and temperature (F0.5 30.3 °C and F10 29 °C) between water depths. To further verify the field result, corrosion rate was measured in laboratory scale. Highest corrosion rate was recorded on the first 7 days of incubation period (L0.5 0.14 mm/year and L10 0.21 mm/year) on medium contained water from 10 m depth. General and pitting corrosion were formed increasingly in accordance with varying pit diameter from small and scattered widely (L0.5) to larger in size (L10). Consequently, HSproduction in both mediums increased during the first 7 days incubation period (L0.5 0.26 mM and L10 0.30 mM) with the appearance of black colored corrosion product (FeS). However, NO3 - concentration plummeted (L0.5 0.18 mM and L10 0.11 mM) after day-21 incubation on both media alongside the production of redbrownish colored corrosion product (FeOH3). SRB growth could be noticed from the production of HS- and black colored corrosion product formation (FeS) on the media, contrast to the NRB growth which consumed NO3 - and yielded redbrownish colored corrosion product. Hence, elaboration on different microbial roles from various water depths in worsening the corrosion process within the research could be categorized as high corrosion risk and diverse corrosion behavior exhibits same corrosion product emergence both field and laboratory scale.