23 Inhibition of Copper Corrosion by Azole Compounds in Acidic Aqueous Solutions 1,2
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R. Johnson , M. Daroux , E. Yeager , and Hatsuo Ishida 1
Macromolecular Science Department, Case Western Reserve University, Cleveland, OH 44106 Department of Chemistry, Case Western Reserve University, Cleveland, OH 44106
Downloaded by RUTGERS UNIV on January 10, 2018 | http://pubs.acs.org Publication Date: October 14, 1986 | doi: 10.1021/bk-1986-0322.ch023
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Azole compounds, poly-N-vinylimidazole (PVI-1) and 2-undecylimidazole (UDI), are studied as alternative inhibitors to benzotriazole (BTA) for copper corrosion in aqueous systems using electrochemical techniques. It is shown that UDI, either as a cast film or dissolved in solution at concentrations as low as 7 x 10 M, inhibits oxygen reduction on copper in acidic solutions of 0.1M HClO (pH=1) while BTA and PVI-1 do not. In phosphate buffer (pH=5.6), UDI and BTA inhibit oxygen reduction on copper, but PVI-1 does not. A l l three compounds suppress the anodic dissolution of copper at pH=1. At pH=5.6, both UDI and PVI-1 cast films produce passivation, UDI reducing the anodic currents by an order of magnitude more than PVI-1, Linear polarization measurements on Cu in UDI solution (pH=5.6) indicate that UDI may have practical application as a corrosion inhibitor for copper. -5
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In the past, heterocycles containing nitrogen have been examined f o r use as i n h i b i t o r s f o r copper (Cu) corrosion [1-25]· To date benzotriazole (BTA), figure 1A, has been the most successful compound and i s widely used i n industry. Recently there has been i n t e r e s t , e s p e c i a l l y i n the printed c i r c u i t board industry [26], i n a l t e r n a t i v e i n h i b i t o r s to BTA that not only i n h i b i t corrosion but also promote adhesion. Imidazoles such as poly-N-vinylimidazole (PVI-1), figure 1B and 2-undecylimidazole (UDI), figure 1C are p o t e n t i a l candidates because imidazoles are commonly used as curing agents f o r epoxy resins and some are reported to i n h i b i t Cu corrosion [26,2J].
BTA i n h i b i t s Cu corrosion i n many aqueous environments [-1-223· The p a r t i a l anodic or cathodic process or processes that are i n h i b i t e d by BTA i s c o n t r o v e r s i a l ; however, most researchers ^Current address: Automotive Research Center, Inmont, 26701 Telegraph Road, Southfield, MI 48086-5009 'To whom correspondence should be addressed 0097-6156/ 86/0322-0250$06.00/0 © 1986 American Chemical Society
Dickie and Floyd; Polymeric Materials for Corrosion Control ACS Symposium Series; American Chemical Society: Washington, DC, 1986.
23. JOHNSON ET AL.
Inhibition of Copper Corrosion by Azole Compounds 251
agree that the mechanism by which BTA acts involves reinforcement of the oxide f i l m . This mechanism i s supported by the poor i n h i b i t i o n of BTA observed at pH6> Ιϊι 12] > where copper oxides are not thermodynamically stable [28]. Acidic conditions, however, are often met i n practice; f o r example i n atmospheric corrosion where evaporation concentration can occur and i n treating baths f o r processing. Inhibitors which are e f f e c t i v e at pH
