Influence of Testing Temperature on the Corrosion Behavior of API 5L X70 Pipeline Steel

Localized corrosion attack is known to take a preponderant role in the onset of stress corrosion cracking of pipeline steels in high pH conditions. Carbonate/bicarbonate solutions can be employed to study the localized corrosion behavior of these materials. In addition to the presence of chloride ions in the electrolyte, the solution temperature is also of prime importance to the onset of pitting corrosion. The aim of this work was to evaluate the influence of the testing temperature on the corrosion behavior of the API 5L X70 pipeline steel which is a standard material for gas pipelines in Brazil. Samples were exposed to a solution consisting of Na2CO3, NaHCO3 and NaCl at three different temperatures: room temperature, 40 oC and 60 oC. The corrosion morphology was observed using scanning electron microscopy. The results showed that pitting corrosion became facilitated when the steel was immersed at higher temperatures.