The work presents an electrochemical study of the corrosion behaviour of two TiC/Cu-Ni metal matrix composites with a content of 10 and 20 wt.% Ni immersed in synthetic seawater. The composites were synthesized by a capillary infiltration technique, obtaining dense materials TiC/Cu-10Ni and TiC/Cu-20 Ni with a residual porosity of 1.8 and 1.7%, respectively. The corrosion rate (CR) was evaluated from the techniques of polarization curves (PC), linear polarization resistance (LPR) and electrochemical impedance spectroscopy (EIS). Electrochemical measurements were carried out under static conditions, ambient temperature and atmospheric pressure at 24 hours exposure in the electrolytic medium. The corrosion rate is affected by the Ni content in the matrix, with less corrosion in the composite with a higher Ni content. The higher content of Ni in the Cu-Ni alloy provides higher passivation and stability to the corrosion products film that are absorbed on the composite surface. Microscopic examination (SEM) showed a characteristic morphology of a corrosion mechanism of the localized type (pits and crevices) generated by a differential aeration, where the TiC/Cu-10Ni composite showed greater degradation.
RESUMENEn el presente trabajo de investigación se estudió el proceso electroquímico de la corrosión en agua de mar sintética de la unión disímil por soldadura fuerte del compósito TiC/Cu. Los compósitos fueron fabricados mediante infiltración líquida sin el uso de presión externa. Dichos compuestos se unieron a cobre usando una aleación de Cu-Ag con adición de Ti en polvo. Estas juntas mostraron una excelente adhesión, formando un ensamble disímil pero coherente. Las pruebas de corrosión empleadas fueron las técnicas electroquímicas de curvas de polarización (CP) y ruido electroquímico (RE). Para determinar el tiempo de estabilización de las reacciones anódica y catódica del proceso de corrosión, se realizó un seguimiento de potencial de corrosión (E corr ) con respecto al tiempo. Las mediciones se realizaron a diferentes intervalos de tiempo, durante un tiempo total de exposición de 24 horas. Las mediciones electroquímicas se realizaron en una celda electroquímica con un arreglo típico de tres electrodos, un electrodo de trabajo, un electrodo de referencia (calomel) y un electrodo auxiliar (barra de grafito). Los resultados electroquímicos muestran que la unión (TiC/Cu-Cu) presenta mayor susceptibilidad a corrosión localizada comparada con el metal base. El mecanismo de corrosión de las uniones se generó por una celda de aeración diferencial producida por corrosión en hendidura y galvánica. Los resultados muestran una buena correlación entre el análisis superficial y los obtenidos por RE y CP.Palabras clave: Corrosión, Compósito, Ruido Electroquímico, Soldadura fuerte. ABSTRACTThis work presents an electrochemical corrosion study in synthetic seawater of the dissimilar joint of TiC/Cu composite by brazing technique. Composites were machined by liquid infiltration without external pressure. This composite were joined with copper using a filler material constituted by an alloy of silver -copper and titanium powder. The composite joined shown a good adhesion forming a dissimilar assembled and coherent. In order to carry out the corrosion studies, two different techniques were used, potentiodynamic polarization curves (PCs) and electrochemical noise (EN). In addition, the corrosion potential measures as a function of the time were carried out to get the stabilization time of the anodic and cathodic reactions in the corrosion process. Electrochemical measurements were made at different exposure times with a total exposure time of 24 hours. A typical three-electrode electrochemical cell was used; where the working electrode (WE) was a sample of composite joined, the reference electrode was the saturated calomel electrode (SCE) and a sintered graphite rod was used as auxiliary electrode. The electrochemical results shown that the susceptibility to localized corrosion of the composite joined sample was higher than the based metal (copper). The corrosion mechanism of the composite joined sample is a differential aeration cell, where it can produce pitting and crevice corrosion form. The results shown a good correlation ...
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