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Role of welding heat tint & surface cleaning on the pitting corrosion of 304&316 austenitic stainless steel in sea water

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dc.contributor.advisorد.فوزى عمر الشاوش
dc.date.accessioned2026-06-08T08:48:28Z
dc.date.available2026-06-08T08:48:28Z
dc.descriptionAustenitic stainless steels are widely used throughout industry in the potable water systems for their corrosion resistance and Food industries, oil petrochemicals industries, many industries. Most surface defects on stainless Steel are produced during the fabrication process (welding heat treatment etc...) and are difficult to remove, thus contributing to the corrosion problems. Common defects included embedded steel particles, Heat tinting, weld spatter all of these tend to initiate corrosion that would not occur so readily in their absence and may accelerated localized corrosion in aggressive environments such as sea water and acid containing environment. Welding of this material introduces a number of variables that can reduce the corrosion resistance and make the material subject to the localized corrosion (pitting). One such variable is the heal tint oxide that is produced during the welding process. This chromium rich layer is considered to be incoherent exposing the chromium depleted, and hence less resistant material to potentially corrosive environment. Literature suggests the pitting resistance of tinted material decreases with an increase in heat tint oxidation. The aim of this study was to test this correlation by producing welded samples (simulated heat tint) produced with different degrees of heat tint and the subject cleaning process or what known as acid pickling as per ASTM A380 standard. This was made to assess the role of heat tint on the susceptibility to the pitting corrosion. While the expected trend was observed within the time frame of the experiments, important inferences on the pitting behavior of heat tinted stainless steel were made. This thesis begins by reviewing the essential effect of simulated heat tint produced by air oxidation over a wide range of temperature 200, 400, 600, 800 and 1050 °C on pitting potential of 304 & 316 Austenitic stainless steel. The study also include the role of alloying elements, pickling time/temperature and all studies were conducted in the sea water environment at room temperature 24±1°C and 50°C. It was found that the heat tint caused marked change in the pitting potential (corrosion resistance) and found to be highly influenced by the heating temperature. Heating at certain temperature such as 600 °C found to cause marked change in the microstructure of stainless steel (304 & 316 SS). This in addition to the heat tint caused marked reduction in the pitting resistance (breakdown pitting potential). Pickling process caused pronounced improve in the corrosion resistance as a result of complete removal of scale from the metal surface. However, the pickling time was observed to be very important factor in improve of corrosion of stainless steel. All pickled samples which were heated at high temperature of 1050 C showed limited improve in the corrosion resistance. This was attributed to the partial removal of the scale from the metal surface when the pickling was conducted for short period of time (adopted pickling time of 15 minutes). Keywords: Stainless steel, surface finish, heat tint, pitting potential, acid pickling.
dc.description.abstractAustenitic stainless steels are widely used throughout industry in the potable water systems for their corrosion resistance and Food industries, oil petrochemicals industries, many industries. Most surface defects on stainless Steel are produced during the fabrication process (welding heat treatment etc...) and are difficult to remove, thus contributing to the corrosion problems. Common defects included embedded steel particles, Heat tinting, weld spatter all of these tend to initiate corrosion that would not occur so readily in their absence and may accelerated localized corrosion in aggressive environments such as sea water and acid containing environment. Welding of this material introduces a number of variables that can reduce the corrosion resistance and make the material subject to the localized corrosion (pitting). One such variable is the heal tint oxide that is produced during the welding process. This chromium rich layer is considered to be incoherent exposing the chromium depleted, and hence less resistant material to potentially corrosive environment. Literature suggests the pitting resistance of tinted material decreases with an increase in heat tint oxidation. The aim of this study was to test this correlation by producing welded samples (simulated heat tint) produced with different degrees of heat tint and the subject cleaning process or what known as acid pickling as per ASTM A380 standard. This was made to assess the role of heat tint on the susceptibility to the pitting corrosion. While the expected trend was observed within the time frame of the experiments, important inferences on the pitting behavior of heat tinted stainless steel were made. This thesis begins by reviewing the essential effect of simulated heat tint produced by air oxidation over a wide range of temperature 200, 400, 600, 800 and 1050 °C on pitting potential of 304 & 316 Austenitic stainless steel. The study also include the role of alloying elements, pickling time/temperature and all studies were conducted in the sea water environment at room temperature 24±1°C and 50°C. It was found that the heat tint caused marked change in the pitting potential (corrosion resistance) and found to be highly influenced by the heating temperature. Heating at certain temperature such as 600 °C found to cause marked change in the microstructure of stainless steel (304 & 316 SS). This in addition to the heat tint caused marked reduction in the pitting resistance (breakdown pitting potential). Pickling process caused pronounced improve in the corrosion resistance as a result of complete removal of scale from the metal surface. However, the pickling time was observed to be very important factor in improve of corrosion of stainless steel. All pickled samples which were heated at high temperature of 1050 C showed limited improve in the corrosion resistance. This was attributed to the partial removal of the scale from the metal surface when the pickling was conducted for short period of time (adopted pickling time of 15 minutes). Keywords: Stainless steel, surface finish, heat tint, pitting potential, acid pickling.
dc.identifier5753
dc.identifier.urihttps://dspace.academy.edu.ly/handle/123456789/2195
dc.subjectالهندسة الميكانيكية والطاقات
dc.titleRole of welding heat tint & surface cleaning on the pitting corrosion of 304&316 austenitic stainless steel in sea water
dspace.entity.typeProject
project.endDate2014
project.funder.nameالتطبيقية والهندسية
project.investigatorعبدالرزاق سالم احمد الشلابي
project.startDate2013
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