Estudo da susceptibilidade à corrosão das ligas API 5L X60 e API5LX80 quando submetidas à fragilização por hidrogênio.

Abstract

The susceptibility to embrittlement by hydrogen in metals and alloys it is common in environments where it is present from cathodic protection, corrosion processes or as gas. His interaction with the crystalline matrix of steel contribute to increase the rate of corrosion, thus facilitating greater penetration of chlorides, water or acid compounds. The weakening of the metal or alloy can also occur from a combination of aggressive effects of cyclic stress, which occur, for example, in the marine environment under the mechanical action of the movement of waves. Several studies have been conducted over time to better understand this mechanism. In this paper we studied the influence of the sub-superficial hydrogen concentration to some parameters such as polarization resistance to corrosion (RP) and annual corrosion rate (CR). To determine the time required for hydrogenation, a computer program was implemented based on the second Fick law, resulting in a time required to obtained a certain concentration of hydrogen. The hydrogen was generated from a solution of 0.1 M NaOH using a potential of 1.300V. Tests of corrosion by linear polarization, were performed using a 0.1 M solution of H2SO4 for the alloys API 5L X60 and X80. The experiments showed that the alloy API 5L X60 has a higher susceptibility to corrosion compared to alloy X80. The latter seems to be more resistant, probably due to the synergistic effect of its components such as boron, nitrogen and aluminum.