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Abstract. The corrosion behavior of mild steel in seawater was investigated using an immersion test and energy-dispersive X-ray spectroscopy in solutions from the sites of Muara Baru, Suramadu and Tol Mandara. As reference, solutions of 3.5% and 5% NaCl were prepared. Dissolved oxygen, salinity, conductivity, and total dissolved solids (TDS) were measured. It was found that uniform corrosion occurred on the mild steel during the immersion test. The corrosion resistance of the steel decreased with increasing exposure time. Since the magnitudes of conductivity, salinity and TDS of all test solutions were similar, it was concluded that dissolved oxygen (DO) and chloride ions play an essential role in inducing the corrosion risk of mild steel. Both parameters hinder the formation of a stable passive film on the surface of corroded mild steel.

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<p><em>The corrosion behavior of mild carbon steel, has been investigated using an immersion test and energy-dispersive X-ray spectroscopy in solutions from the sites of Karangsong and Eretan, Northern Coast of West Java Region, Indonesia. As reference, solutions of 3.5% and 5% NaCl were prepared. Salinity, conductivity, and total dissolved solids (TDS) were measured. It was found that uniform corrosion observed on mild steel during the immersion test. Corrosion resistance of alloys decreases with increasing exposure time in natural seawater solutions. Since magnitudes of conductivity, salinity and TDS of all test solutions are similar, it implied that chloride ion have primary role for inducing the corrosion risk of mild steel. That parameter hinders the formation of stable passive film on the surface of corroded mild steel.</em></p><p><strong>Key words:</strong> <em>conductivity; immersion test; mild steel; salinity; seawater; total dissolved solids</em>.</p>

The investigation of corrosion for carbon steel and galvanized steel has been conducted in the marine atmosphere of Eretan and Ciwaringin Districts, West Java Province. The exposure time of the field test was up to 200 days, and their corrosion rates are determined according to weight loss method. The objective of the work is to elucidate the corrosion behavior of those alloys which is affected by distances from coastline and environmental condition. The magnitude of corrosion rate for carbon steel was 20 times as high as that for galvanized steel in both districts The distance from coastline has significantly affected for the magnitude of corrosion rate, where that both alloys in Ciwaringin is lower than that in Eretan. The deposition of chloride ion in Eretan and Ciwaringin Districts were 4.305 mg/m2 day and 1.863 mg/m2 day, respectively, where the higher chloride ion can tend to increase the corrosion rates. Relative humidity (RH) which is over 60% has essential role for corrosion process as well as rainfall. The uniform corrosion attack was observed both alloys after exposure. The corrosion product phases of galvanized steel exhibits as zincite, hydrozincite and simonkolleite in Eretan as the typical coastline atmosphere phases but not in Ciwaringin. The formation of rust product for both metals lead the decrease of further corrosion attack due to the barrier between metal and environment. The usage of galvanized steel is remarkable to minimize corrosion attack compared to that of carbon steel in tropical coastline.

The corrosive destruction of steel as material of maritime infrastructure had been investigated using simulated wet-dry test, loss weight, energy dispersive X-Ray spectroscopy (EDS) and X-ray diffraction (XRD) in seawater solutions of Muara Baru,Jakarta; Karangsong and Eretan regions, Indramayu. Controlled solution used as the comparison of natural seawater are 3,5% NaCl and 5% NaCl. The results shows that uniform corrosion took place on carbon steel after the exposure. The resistance of corrosion increases rapidly on the first 7 days, then decreases with increasing exposure time. The effect of conductivity, salinity and total dissolve solids (TDS) of test solutions for steel corrosion process was almost same at each interval of exposure time. The decrease of dissolved oxygen (DO) enhances corrosion rate on the first 7 days, which indicated the formation of oxide layer as the further barrier of corrosion process. The role of high concentration for chloride ion increases corrosion rate after 7 days of exposure time, which interfere the forming of stable oxide layer on the metal surface. That interference induces corrosion rate tends to increase again. The compound of γ FeO(OH) (Lepidrococite) formed as predominant corrosion product.