Effect of 10% NaCl on basic carbon structural P235TR2 steel at 10^oC

Abstract

Metal alloys working in real conditions are exposed to aggressive environments. The degree of aggressiveness of the environment may vary. Therefore, various construction materials are used to build machines and devices. One of the groups of materials widely used in industry are low-carbon steels. They owe their popularity mainly to the low price and relatively good technological and functional properties. These steels usually work in a low-aggressive environment. Pipelines are a typical application for low carbon steels. Pipelines are protected from corrosion on the outside, while the inside (working side) is not protected. One of the media in the pipelines is a liquid with a low concentration of NaCl. Pipelines are usually located underground, so their operating temperature is almost constant in the annual cycle and amounts to approx. 10 °C. Taking the above into account, tests were carried out on one of the most frequently used steel grades, P235TR2, for the construction of pipelines. The tests were carried out at a temperature of 10 °C in a 10% NaCl aqueous solution. After preparation, the samples were soaked in a corrosive solution for up to 432 hours. Corrosion loss was determined by the gravimetric method. Relative corrosion and corrosion rate of steel in the tested medium were calculated. On the basis of the tests carried out, it was found that P235TR2 steel has good corrosion resistance in the environment of 10% NaCl at 10 °C. The corrosion was divided into two stages. In the first, a slow progress of the corrosion process was noted, in the second, a gradual increase in the corrosion rate was noted. The increase in the corrosion rate is the result of the surface development that occurs as a result of corrosion. With the possibility of contact of the corrosive medium with a larger surface, even with the constant impact of the corrosive agent, there is a greater corrosion loss, which translates into an increase in the rate of corrosion.