REACTIVIDAD SUPERFICIAL DE FUNDICIONES NODULARES. INFLUENCIA DE LA MICROESTRUCTURA Y DEL CONTEO NODULAR.

A.D. SOSA, M.D. ECHEVERRIA, O.J. MONCADA, S. SIMISON

Fortaleza, Brasil

Congreso; Congresso Latino Americano de Corrosao; 2006

Associacao Brasileira de Corrosao (ABRACO)

The usage of thin wall ductile iron casts is rising steadily. The decrease of cast thickness promotes a strong increase on the nodular count, which influences different properties of the material. On the other hand, a wide range of mechanical properties can be obtained by heat treatments. Corrosion resistance is highly dependent on the quantity and distribution of phases of different electrochemical nature. The aim of this paper is to analyze the effect of nodular count and microstructure on surface reactivity on ductile iron samples with nodular counts ranging from 260 to 1500 nodules/mm2. The microstructures are: ferrictic, ferritic-pearlitic and ausferritic (ADI). Surface reactivity was characterized by means of chronoamperometric tests in a three electrodes cell and 3.5% NaCl solution. Differences in the dissolution rate were found. Results indicate increasing surface reactivity for higher nodular counts. As regard the microstructure, ADI samples show the lowest values of dissolution rate and the presence of a low hardness surface layer where the microstructure is revealed.