CLEANING OF 200 YEAR-OLD COPPER WORKS-OF-ART USING CITRIC-ACID WITH AND WITHOUT BENZOTRIAZOLE AND 2-AMINO-5-MERCAPTO-1,3,4-THIADIAZOLE

This paper studies the use of 5% (wt) citric acid without inhibitor, i nhibited with benzotriazole (BTA) and 2-amino-5-mercapto-1,3,4-thiadia zole (AMT) and de-aerated with nitrogen in the cleaning of 18th and 19 th century chalcographic plates. DC and AC electrochemical techniques have been used to characterize the effect of the inhibitors and to qua ntify the aggressiveness of the cleaning treatment. Citric acid remove s copper surface tarnish. BTA and AMT inhibitors are similarly efficie nt. De-aeration reduces corrosion to levels similar to those obtained with inhibitors.