Corrosion of 5456-H117 Aluminum in High Velocity Sea Water

“…Localized flow conditions on these pits and hydrodynamic shear stresses shear the particles off and remove the galvanic cell, leading to a decrease in the pitting corrosion rate. They also believe that the form and rate of corrosion of aluminum under hydrodynamic conditions depend on flow velocity [8,9]. However, research by the authors showed that, at high speeds, pits covered a larger portion of the surface.…”

Section: Introductionmentioning

confidence: 96%

“…Some researchers believe that increasing flow rates in seawater reduces the possibility of pitting observed in stagnant and low flow rate environments, while the rate of uniform corrosion increases [7,8]. Davis and Ghering believe that under flowing conditions, due to disruption and removal of the oxide layer on particles of intermetallics, pitting corrosion occurs at those locations.…”

Section: Introductionmentioning

confidence: 96%

Novel approach using EIS to study flow accelerated pitting corrosion of AA5083-H321 aluminum–magnesium alloy in NaCl solution

2009

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EIS was utilized as a novel approach to study the role of mechanical and electrochemical processes in flow accelerated pitting corrosion behaviour of AA5083-H321 aluminum-magnesium alloy in 3.5% NaCl solution. This alloy is a suitable material for manufacturing of high speed boats, submarines, desalination systems etc. Impedance spectra were obtained during 24 h of exposure of the samples to the test solution at different rotation speeds. The surface and cross section of the samples were studied by scanning electron microscopy (SEM) and EDAX analysis. The results indicated that increasing the rotation speed causes the depth of pits to increase. By further increasing the rotation speed to 5 and 7 m s -1 , the flow condition causes the passive layer inside the pits to breakdown. Simultaneously, the thickness of the passive layer on the areas other than the pits becomes thinner. Shear stresses at 10 m s -1 are so severe that the passive layer on the entire surface breaks down and leads to micropitting corrosion.

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“…Previous works show that the Al 6 (Fe, Mn) phase has more noble potential relatively to aluminium [6] and, thereby, the cathodic reactions have being taking place there are responsible for pitting formation in the surrounding alloy matrix [7].…”

Section: Introductionmentioning

confidence: 99%