The corrosion rate of 90/10 and 70/30 Cupronickels and Al-Brass in different organic acid and complexing agent solutions was determined in conditions similar to that of the heat exchangers cleaning. Tests were performed in the following solutions: 10% EDTA (pH adjusted at 5, 7, 9 by addition of ammonia); 3% citric acid; 3% ammoniated citric acid (pH = 3.5); 1.5% formic acid + 1.5% hydroxyacetic acid mixture. The organic compounds tested as inhibitors, at 1mM concentration, were 2-mercaptopyrimidine (2McPy), 5-mercapto-1-phenyl-tetrazole (5Mc1PhT) and 1,3 bis(pyridyl-methyl)-2-thiourea (BisPyTU). Corrosion rate was determined by weight loss tests of 6 hours at 90°C. Anodic and cathodic polarisation curves were recorded in the uninhibited and inhibited solutions, at 60°C, starting from the corrosion potential assumed by the electrodes after 1 hour of immersion in the solutions. The corrosion rate of the three alloys in the different solutions was found to be very low and only in 10% EDTA pH = 5 solution was it higher than 0.1 mg/cm2 h. Inhibition tests performed in the last solution showed that the best corrosion inhibitor for the three alloys was 5Mc1PhT, followed by 2McPy. The polarisation curves showed that the compounds examined acted on the cathodic reduction process and mainly on the anodic disssolution of the alloys. The results showed that the copper alloys can be cleaned in organic acids and in complexing agent solutions with corrosion rate of about 0.1 mg/cm2 h. When the corrosion rate was higher than 0.1 mg/cm2 h , 2McPy or 5Mc1PhT at 1mM concentration can be used as excellent inhibitors.

Cleaning of copper alloys in organic acids and complexing agent solutions.

ZUCCHI, Fabrizio;TRABANELLI, Giordano;GRASSI, Vincenzo
1998

Abstract

The corrosion rate of 90/10 and 70/30 Cupronickels and Al-Brass in different organic acid and complexing agent solutions was determined in conditions similar to that of the heat exchangers cleaning. Tests were performed in the following solutions: 10% EDTA (pH adjusted at 5, 7, 9 by addition of ammonia); 3% citric acid; 3% ammoniated citric acid (pH = 3.5); 1.5% formic acid + 1.5% hydroxyacetic acid mixture. The organic compounds tested as inhibitors, at 1mM concentration, were 2-mercaptopyrimidine (2McPy), 5-mercapto-1-phenyl-tetrazole (5Mc1PhT) and 1,3 bis(pyridyl-methyl)-2-thiourea (BisPyTU). Corrosion rate was determined by weight loss tests of 6 hours at 90°C. Anodic and cathodic polarisation curves were recorded in the uninhibited and inhibited solutions, at 60°C, starting from the corrosion potential assumed by the electrodes after 1 hour of immersion in the solutions. The corrosion rate of the three alloys in the different solutions was found to be very low and only in 10% EDTA pH = 5 solution was it higher than 0.1 mg/cm2 h. Inhibition tests performed in the last solution showed that the best corrosion inhibitor for the three alloys was 5Mc1PhT, followed by 2McPy. The polarisation curves showed that the compounds examined acted on the cathodic reduction process and mainly on the anodic disssolution of the alloys. The results showed that the copper alloys can be cleaned in organic acids and in complexing agent solutions with corrosion rate of about 0.1 mg/cm2 h. When the corrosion rate was higher than 0.1 mg/cm2 h , 2McPy or 5Mc1PhT at 1mM concentration can be used as excellent inhibitors.
copper alloys; cleaning; organic acids; complexing agents; inhibitors
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11392/1196538
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