Optimizing the preparation procedure of self-assembled monolayer of stearic acid for protection of cupronickel alloy.

The aim of this work is to examine the possibility of CuNi protection in chloride media by self-assembled monolayers (SAMs) of stearic acid (SA). In order to obtain a compact, well ordered monolayer, that will provide long term protection, different SAM preparation procedures are studied. The influence of CuNi pretreatment, SA solution temperature and temperature of the drying period followed after the SA treatment on the protective properties of stearic acid self-assembled layer are examined by electrochemical methods and surface analysis techniques. The obtained results show that for complete self-assembled film formation it is necessary to have a drying period after exposing the sample to the stearic acid solution. Heating of the SA solution and drying period at higher temperatures result in layers with better stability in chloride media. The most compact surface layer, that provides long lasting and efficient protection to the underlying alloy, is obtained when prior to SA solution exposure an oxide layer on CuNi surface was formed at elevated temperatures.