Evaluation of Hydroxyethane Diphosphonic Acid (HEDPA) as Metal Cleaning Agent Using Chemical and Electrochemical Test Methods: Part I

摘要

In order to evaluate the adaptability of hydroxyethane diphosphonic acid (HEDPA) as an environmentally benign alternative rust removal agent, a systematic investigation is being carried out. The effectiveness of 2 vol.% (0. 082 M) HEDPA was thoroughly investigated in the temperature range 27 - 60 deg C. The results suggest that the acid, HEDPA, is very effective in the rust removal process. It was found that the rust was completely removed by the HEDPA within 3 hours at 27 deg C, or within 30 minutes at 60 deg C. The rust dissolution process was found to have an activation energy of 11 +/- 1 kcal/mole. Prolonged treatment of samples with HEDPA results in the re-deposition of the reaction products onto the cleaned sample surface. The reaction product appears to be a mixture of complex higher order iron phosphates.