Detección de la corrosión por picadura en aceros inoxidables empleando ultrasonidos

Abstract

RESUMEN:Los sistemas pasivables, capaces de desarrollar una capa protectora, delgada, adherente y continua sobre el substrato metálico, presentan excelente resistencia a la corrosión ya que dicha capa se produce instantáneamente al reaccionar con el medio. Ahora bien, en determinadas circunstancias, esa capa se puede romper localmente, dando lugar a uno de los ataques más insidiosos que se conocen, corrosión por picadura, que producen unas condiciones químicas locales que aceleran el proceso corrosivo provocando defectos en el material, tanto externos como internos, con una distribución aleatoria en la superficie metálica. En este trabajo se ha planteado el empleo de técnicas de ensayos no destructivas mediante ultrasonidos para detectar este tipo de ataque en un acero inoxidable austenítico AISI 304, con distinta distribución superficial de defectología y profundidades de ataque, que simulan picaduras, tomando como variable fundamental de la onda ultrasónica la amplitud máxima del eco de fondo. SUMMARY:Pitting corrosion detection in stainless steels using ultrasounds. Passive metallic systems are able to develop in a spontaneous way a protective layer on the metallic surface that offers excellent corrosion resistance since really in a physical barrier for the reaction with the environment. However, some factors can break locally this layer, promoting one of the most insidious attack, pitting corrosion, which produces local chemical conditions that favouring the corrosive process causing defects in the material, as externals and internals ones, with a random distribution on the metal surface. In this work, ultrasounds non destructive technique has been employed using as variable the maximum amplitude of the backwall echo in order to detect this type of attack. The material employed is an austenitic stainless steel AISI 304, wherein appear several defectology distributions as superficial such as depths simulating pits.

Pitting Detection and Characterization From Ultrasound Timelapse Images Using Convolutional Neural Networks

“…The shape of the pit is triangular and similar to what would be expected if a 2.2 mm drill bit with a cutting tip of 135°w as used. A conical morphology like this is a reasonable approximation for how an initial attack by pitting corrosion might occur, so there is a resemblance between the real pitting, the machined equivalent, and the simulated case [22], [23].…”

“…Jarvis et al [16] demonstrate how small pits impact the reflected back-wall amplitude and pulse shape through simulated and real experiments. Echo amplitude was the basis of the analysis of pitting depth and diameter by Rodrígues and Biezma [17]. Pitting detection has much in common with general flaw detection, and one of the challenges is separating the reflection from the flaw near a surface and the surface reflection itself.…”

Erosion behavior of 440C stainless steel cryogenically treated

“…Stainless steels have numerous applications in different industrial sectors due to its excellent mechanical properties besides its easy forming processes and competitive price (Rodríguez et al, 2014), some studies are, AISI-304 (López-Martínez et al, 2013) and AISI-410 (Cuevas-Arteaga et al,2019). AISI-440C belongs to the martensitic group because of its transformation from austenite to martensite produced by the quenching from the austenite phase (Aguinaco -Bravo et al, 1999), is considered as a high carbon steel with good resistance to deterioration and good mechanical properties.…”