ABSTRACT

The potential and current oscillations during pitting corrosion of steel in NaCl solution were studied. Detailed analysis using numerical diagnostics developed to characterize complex time series clearly shows that the irregularity in these time series corresponds to deterministic chaos, rather than to random noise. The chaotic oscillations were characterized by power spectral densities, phase space and Lyapunov exponents.

INTRODUCTION

Electrochemical Noise(EN) is a tool both for the mental understanding of various aspects of corrosion and for the solution of practical problems of corrosion protection, in particular in the area of corrosion monitoring?. A characteristic feature of EN measurements in comparison with other electrochemical methods for investigating corrosion is that the information is obtained without perturbing the system to be measured. The high sensitivity of the technique also permits detection of the initiation of localized corrosion on passive metal surfaces.

We have recently established a research project to determine the mechanisms and the factors influencing the deterioration of thin plasma polymerized films deposited on to carbon steel substrates. Plasma polymerizationis a technique for applying thin, highly cross linked polymerfilms to materials by exposing the materials to a plasma excited in a monomer. The method has potential as an environmentally compatible process for the application of polymer matings to metals and other materials. Boerio and co-workers have been examining plasma polymerized coatings for metals, as, for

Instance ,pretreatment for adhesive bonding of aluminum and steel .As a first step, we present in this communication the electrochemical current and potential noise response of the metallic substrate without any plasmapolymerizedfilm.

The aim of the present study has been to analyze the electrochemical noise measured on steel in NaCl solution by the use of various mathematical tools from the thecnyofchaos in order o characterize the mechanism of different types of corrosion.

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