Semiconducting Behavior of Organic Polymer Coatings in 5% Sodium Hydroxide Solution

The semiconducting behavior of organic polymer coatings in 5% sodium hydroxide solution was studied by potential-capacitance and Mott-Schottky analysis.It was pointed out that the capacitance of space charge layer(Csc) of organic polymer coatings was much lower than that of carbon steel.With the increase of immersion time in the solution,the Csc of organic polymer coatings increased gradually,and the thickness of space charge layer decreased gradually.In the solution,the polymer coatings showed different semiconducting behaviours,i.e.,the polymer of epoxy resin was an insulator,while phenol aldehyde resin and alkyd resin were bipolar films;At potential range of -0.3~0 V,the coatings showed a p-type semiconductor;At potential range of 0~0.4 V,the coatings showed a n-type semiconductor.The concentration of charge carriers in the polymer coatings increased along with increasing immersion time.