US EPA

3221119 

Journal Article 

Evaluation of the protective properties of natural and artificial patinas on copper. Part I. Patinas formed by immersion 

Rosales, B; Vera, R; Moriena, G 

1999 

Yes 

Corrosion Science
ISSN: 0010-938X
EISSN: 1879-0496 

41 

4 

625-651 

WOS:000079025300001 

The variable character of the ambient parameters determine
different passivating properties of the corrosion products formed during outdoor exposure. Three
year tests, at least, are necessary in the atmosphere where the patina should be naturally
formed, to have long term information about the protectiveness it can develop, its stabilisation
rate and the morphology of the attack suffered by the metal. Patinas formed in laboratory, on the
contrary, can have well defined chemical composition and morphology, allowing accelerated
formation through uniform attack, with controllable corrosion rate of the metal. The protective
properties of the corrosion products of copper forming light blue, green, purple and brown
artificial patinas and of patina naturally formed during outdoor exposure were evaluated through
different characterisation techniques. Potentiokinetic polarisation, scanning electron microscopy
(SEM) and EDX surface analysis were applied on the weathered metal samples. The composition of
the corrosion products was determined through X ray diffraction and IR spectroscopies. Comparison
of the results allowed the classification of the green patina, among the artificial and the
naturally formed by outdoor exposure, as the best, from the protective properties point of view.
The other 3 presented different failures, consisting of poor adherence, high porosity and
exfoliation of the underlying metal. (C) 1999 Elsevier Science Ltd. All rights reserved.