Análisis de los transitorios de ruido electroquímico para aceros inoxidables 316 Y – DUPLEX 2205 en NaCl Y FeCl

Abstract

La película de óxido formada en la superficie de materiales como los aceros inoxidables, así como de aleaciones base níquel, aluminio, titanio, cobre y otros metales, es la responsable de su alta resistencia a la corrosión. Sin embargo, la resistencia de la película pasiva está determinada por las condiciones ambientales a que está expuesto el material, así como por la composición de la aleación [1] . Al incrementar la concentración de los iones agresivos, especialmente iones cloruro Cl -, también aumenta el ataque por picaduras [2], y causan que las películas pasivas sean susceptibles al rompimiento localizado, resultando en una disolución acelerada del metal [3] , principalmente en los sitios donde existen irregularidades en la superficie del material, produciendo la corrosión localizada, principalmente corrosión por picaduras en los aceros inoxidables [4 y 5] .Como parte de las técnicas electroquímicas, se encuentra el Ruido Electroquímico (EN), que es una técnica no destructiva [6] , y que refleja la suma individual de los eventos aleatorios de las fluctuaciones ResumenEn este trabajo se muestran los resultados obtenidos de las mediciones de ruido electroquímico para diferentes materiales que exhiben corrosión por picaduras. Los transitorios presentados en las series de tiempo en corriente y en potencial, se correlacionan con el análisis superficial de microscopía electrónica de barrido (MEB). Las mediciones electroquímicas fueron realizadas a diferentes tiempos de exposición, para obtener una correlación. Los materiales usados fueron los aceros inoxidables 316 y dúplex 2205, inmersos en cloruro férrico (FeCl 3 ) y cloruro de sodio (NaCl) como electrolitos. Los análisis por MEB, muestran que los transitorios observados en las series de tiempo, corresponden realmente con la actividad de la nucleación de picaduras desarrollada sobre la superficie de los electrodos. Palabras claveCorrosión por picaduras; Ruido electroquímico; Técnicas electroquímicas; Acero inoxidable austenítico 316; Acero inoxidable Dúplex 2205. Electrochemical noise transient analysis for 316 and Duplex 2205 stainless steels in NaCl and FeCl AbstractThis work shows the results obtained from electrochemical noise measurements for different materials exhibiting pitting corrosion. The transients presented in the potential and current time, correlates with the scanning electron microscopy (SEM) surface analysis. Electrochemical measurements were made at different exposure times to obtain the correlation. The materials used were stainless steel austenitic 316 and duplex 2205, immersed in ferric chloride (FeCl 3 ) and sodium chloride (NaCl) electrolytes. SEM analysis shows that the transients observed in the time series, really correspond to the activity of pit nucleation developed over the surface of the electrodes.

Corrosion of API X80 Steel Immersed in Seawater: Application of Electrochemical Noise Technique

“…An alternative technique, which is increasingly used, is the Electrochemical Noise (EN) (9), which is a non-destructive technique since it does not require applying an external voltage to obtain a measurable response and basically registers simultaneously spontaneous fluctuations of current and potential produced by the microcells formed on metal surface that is corroding (10). In this technique, electrochemical potential noise is measured as the fluctuation in potential of a working electrode with respect to a reference electrode or as the fluctuation in potential difference between two nominally identical working electrodes and electrochemical current noise is generally measured as the galvanic coupling current between two nominally identical working electrodes, with the current being measured using a zero resistance ammeter (ZRA) to ensure that the two electrodes are at the same electronic potential (11).…”

Frequency Analysis of Transients in Electrochemical Noise of Superalloys Waspaloy and Ultimet

“…It is necessary to separate DC from random and stationary components to analyze EN data because DC creates false frequencies and interferes in visual, statistical, and PSD analysis. In this way, when DC is removed, corrosion data presented at low frequencies are conserved [43][44][45][46][47][48][49]. In the EN time series, there are three components: DC signal, Random, and Stationary.…”

Electrochemical Noise Measurements of Advanced High-Strength Steels in Different Solutions

“…A decrease in potential signal with lower amplitude and higher frequency transients as time increases could indicate a passive state, in effect, these trends appear because passive systems are highly polarizable, therefore small changes in current produce high changes in the potential signal. Another possible reason to explain this trend is the development of metastable pits which can be formed below the pitting potential [56].…”

“…Similarly, three-tending values were calculated for the kurtosis parameter. In the case of skewness, the range would indicate that the data distribution is moderately skewed and in case of kurtosis it would indicate a Gaussian or normal distribution [56]. In the same reference it was associated that uniform corrosion follows a Gaussian distribution.…”