Reference
W. Neagle - NACE March 11th - 15th, 1991, paper no. 568
Abstract
The role of HYDROXY PHOSPHONOACETIC ACID (HPA) in the inhibition of mild steel corrosion in aqueous systems, has been elucidated by the use of a range of physicochemical techniques. In particular, surface analytical studies have clarified the form and the structure of the protective layer.
Conclusion
- HPA forms an inhibitive film involving its trianionic ion and calcium.
- Calcium facilitates transport and adsorption of HPA by the formation of a solution complex of neutral charge.
- The film formed by HPA and calcium inhibits the cathodic oxygen reduction reaction on mild steel.
- The film is self-limiting as the driving force for film growth is high pH due to oxygen reduction.
- The film formed is around 20-80 nm thick - enough to offer excellent excellent protection without interfering with heat transfer.