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RESEARCH ARTICLE
Contents Vol 61(6)

Direct-Current Methods for the Estimation of Corrosion Rates in Aqueous Timber Preservatives

Gareth Kear A B D , Hãi-Zhèn Wú A , Mark S. Jones A and Frank C. Walsh C
+ Author Affiliations
- Author Affiliations

A Building Research Association of New Zealand (BRANZ) Ltd, Science and Engineering Services, Private Bag 50 908, Porirua City 5240, New Zealand.

B Present address: Electrochemical Engineering Laboratory, Energy Technology Research Group, School of Engineering Sciences, University of Southampton, Highfield, Southampton SO17 1BJ, UK.

C Electrochemical Engineering Laboratory, Energy Technology Research Group, School of Engineering Sciences, University of Southampton, Highfield, Southampton SO17 1BJ, UK.

D Corresponding author. Email: g.kear@soton.ac.uk

Australian Journal of Chemistry 61(6) 455-465 https://doi.org/10.1071/CH07429
Submitted: 13 December 2007  Accepted: 11 May 2008   Published: 19 June 2008

Abstract

As part of a program to assess the durability of metals in timber preservatives, direct-current electrochemical analyses have been carried out using mild steel, American Iron and Steel Institute 316 stainless steel and galvanized steel immersed in three liquid timber preservatives containing dissolved copper as a biocide. The aqueous preservatives examined were copper–chrome–arsenate (Cu–Cr–As), copper azole (Cu-Tebucanazole), and alkaline copper quaternary (Cu-didecylthyl ammonium chloride). These preservatives are known commercially as CCA, CuAz, and ACQ-B, respectively. Despite previous assumptions, neither polarization resistance- nor Tafel slope-based analyses are suitable methodologies for the universal derivation of absolute values of corrosion rate. An alternative approach is suggested based on anodic linear sweep voltammetry. The results show that the hot-dipped zinc coating was found to be the most active material in terms of the polarization behaviour, especially within the CCA-based electrolyte. There is a strong qualitative correlation between the electrochemical data and corrosion rates estimated using the American Wood Preservers’ Association E-17 standard test for aqueous treatment solutions.


Acknowledgements

The present work was performed in the laboratories of BRANZ Ltd (New Zealand) and funded by the New Zealand Building Research Levy. Concentrations of aqueous copper in the preservative concentrates were determined by Spectrachem Analytical Ltd (New Zealand).


References


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[52]   ASTM G5 Standard Reference Test Method for Making Potentiostatic and Potentiodynamic Anodic Polarization Measurements 1994 (ASTM International: West Conshohocken, PA).

[53]   ASTM G59 Standard Test Method for Conducting Potentiodynamic Polarization Resistance Measurements 1997 (ASTM International: West Conshohocken, PA).