Use of ethylenediamine disuccinic acid in metal surface treatment

Abstract

Hydrogen embrittlement is a continuing problem in the cleaning of metal surfaces. Furthermore, current processes often use strong acids and can have a poor environmental profile. Work is reported to show that ethylenediamine disuccinic acid (EDDS) offers an alternative process medium for a range of metals. The cleaning of the metal surface is environmentally friendly under mild conditions and does not result in hydrogen embrittlement. Rust removal from an iron surface can be achieved at neutral pH using EDDS at a low concentration. EDDS was found to be effective in hard water whereas the effectiveness of other chelants may be reduced by ions causing hardness. The results are consistent with the stability constants for metal ions which indicate that EDDS is selective for iron. Initial studies on aluminium have demonstrated that EDDS can remove metal deposits from an aluminium surface. Operation in neutral conditions means hydrogen is not generated, removing any risk of embrittlement. EDDS also offers some corrosion inhibition of aluminium and does not produce discoloration of the surface.

Keywords:

• Iron
• Aluminium
• EDDS
• Rust removal
• Corrosion
• Cleaning

This paper is based on a presentation given at the TransFair 2013 conference held at The Heritage Motor Centre, Gaydon, Warwickshire, UK, on 11–13 June 2013.