In this study an accelerated ageing has been performed on copper sheets successively submitted to different recovering and stabilizing treatments. The accelerated ageing has been carried out in a climatic chamber for three months with thermal cycles simulating the weather of a desertic country like Egypt (12 h at 60°C with 50% of relative Humidity followed by 12 h at 10°C with 90% of relative humidity) with carbon dioxide flowing; the samples werre buried in silica sand with the addition of sodium chloride in the average amounts of Egyptian sands (about 4 wt%). On the aged samples the presence of cuprite and copper basic chloride has been detected by X-ray diffraction. The cleaning techniques employed were: intensive distilled water rinsing, immersion in dilute aqueous sesquicarbonate solution (the solution has been changed until no more chloride was detected), alternate immersions in hydrated ammonia 32% and methyl alcohol (10:90 by volume) solution, and hydrogen peroxide 36 vol. and methyl alcohol (10:90 by volume) solution, and finally, for comparison purposes, electrolysis for total stripping of the corrosion products. The stabilisation was performed by immersion in 0.01M acqueous solution of 5-amino 2-mercapto- 1,3,4-thiadiazole (AMT) at 60°C followed by repeated washing in water, another set of samples was dipped in a traditional inhibiting solution, 1H-benzotriazole (BTA) in acetone. The effectiveness of the recovering and stabilization processes has been evaluated by means of 10 and 30 days exposures to three aggressive environments (salt spray, humidostatic chamber, climatic chamber with thermal cycles simulating the climate of unconditioned museum exhibition rooms) and by means of electrochemical tecniques (free corrosion potential and polarization resistance measurements, recording of polarization curves). The results obtained allow to state that the most suitable recovering and stabilizing techniques seem to be treatments with BTA and AMT inhibiting compounds and that the electrochemical tecniques may be usefully employed to obtain quick indications on the effectiveness of recovering techniques.
A comparative study of methods for the assesment of recovery techniques for aged copper
ZUCCHI, Fabrizio
1995
Abstract
In this study an accelerated ageing has been performed on copper sheets successively submitted to different recovering and stabilizing treatments. The accelerated ageing has been carried out in a climatic chamber for three months with thermal cycles simulating the weather of a desertic country like Egypt (12 h at 60°C with 50% of relative Humidity followed by 12 h at 10°C with 90% of relative humidity) with carbon dioxide flowing; the samples werre buried in silica sand with the addition of sodium chloride in the average amounts of Egyptian sands (about 4 wt%). On the aged samples the presence of cuprite and copper basic chloride has been detected by X-ray diffraction. The cleaning techniques employed were: intensive distilled water rinsing, immersion in dilute aqueous sesquicarbonate solution (the solution has been changed until no more chloride was detected), alternate immersions in hydrated ammonia 32% and methyl alcohol (10:90 by volume) solution, and hydrogen peroxide 36 vol. and methyl alcohol (10:90 by volume) solution, and finally, for comparison purposes, electrolysis for total stripping of the corrosion products. The stabilisation was performed by immersion in 0.01M acqueous solution of 5-amino 2-mercapto- 1,3,4-thiadiazole (AMT) at 60°C followed by repeated washing in water, another set of samples was dipped in a traditional inhibiting solution, 1H-benzotriazole (BTA) in acetone. The effectiveness of the recovering and stabilization processes has been evaluated by means of 10 and 30 days exposures to three aggressive environments (salt spray, humidostatic chamber, climatic chamber with thermal cycles simulating the climate of unconditioned museum exhibition rooms) and by means of electrochemical tecniques (free corrosion potential and polarization resistance measurements, recording of polarization curves). The results obtained allow to state that the most suitable recovering and stabilizing techniques seem to be treatments with BTA and AMT inhibiting compounds and that the electrochemical tecniques may be usefully employed to obtain quick indications on the effectiveness of recovering techniques.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
