Korean Institute of Surface Engineering

pISSN : 1225-8024 | eISSN : 3399-8403


공학

한국표면공학회지 (36권4호 301-306)

A Study of Localized Corrosion Mechanisms in the Multilayered Coatings by Cathodic Arc Deposition

음극아크증착법으로 합성한 다층박막의 국부부식 기구에 관한 연구

김호건;안승호;이정호;김정구;한전건;

성균관대학교 신소재공학과;

Abstract

Multilayered WC-Ti/suv $1-x/Al_{x}$ N coatings were deposited on AISI D2 steel using cathodic arc deposition (CAD) method. These coatings contain structural defects such as pores or droplets. Thus, the substrate is not completely isolated from the corrosive environment. The growth defects (pores, pinholes) in the coatings are detrimental to corrosion resistance of the coatings used in severe corrosion environments. The localized corrosion behavior of the coatings was studied in deaerated 3.5 wt.% NaCl solution using electrochemical techniques (potentiodynamic polarization test) and surface analyses (GDOES, SEM, AES, TEM). The porosity was calculated from the result of potentiodynamic polarization test of the uncoated and coated specimens. The calculated porosity is higher in the $WC-Ti_{0.6}$ $Al_{0.4}$ N than others, which is closely related to the packing factor. The positive effects of greater packing factor act on inhibiting the passage of the corrosive electrolyte to the substrate and lowering the localized corrosion kinetics. From the electrochemical tests and surface analyses, the major corrosion mechanisms can be classified into two basic categories: localized corrosion and galvanic corrosion.

Keywords

Porosity;packing factor;Galvanic corrosion;Localized corrosion;Droplet;