Corrosion of ferrous- and zinc-based materials in CCA, ACQ and CuAz timber preservative aqueous solutions

• Published in: Materials and structures Vol. 41; no. 8; pp. 1405 - 1417
• Main Authors: Kear, Gareth, Wú, Hăi-Zhèn, Jones, Mark S.
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01.10.2008; Springer; Springer Nature B.V
• Subjects: ANODES; Applied sciences; Aqueous solutions; Austenitic stainless steels; Building construction; Building Materials; Building structure; Buildings. Public works; Carbon steels; CATHODES; Civil Engineering; Construction (buildings and works); Copper; CORROSION; Corrosion tests; Durability. Pathology. Repairing. Maintenance; Electrolytes; Engineering; Exact sciences and technology; Machines; Manufacturing; Materials; Materials Science; Metallic materials; Original Article; Paints and renderings. Protection products; PRESERVATIVES; Processes; Solid Mechanics; SOLUTIONS; STEELS; Structural steels; Theoretical and Applied Mechanics; Timber; Wood structure; CCA; Mild steel; Corrosion; Mass loss; Aqueous timber preservative; Hot-dipped galvanised steel; CuAz; 316 Stainless steel; ACQ; Material processing; Preservation; Galvanized steel; Corrosion rate; Bolt; Mild steel, Mass loss; Metal; Wood construction; Experimental study; Nail; Stainless steel; Corrosion test; Aqueous solution; Copper; Aqueous timber preservative, Corrosion, CCA
• ISSN: 1359-5997; 1871-6873
• DOI: 10.1617/s11527-007-9338-6

Timber construction relies on connections between members. Traditionally, metallic nails and bolts are used for this. Previous research has shown that these metallic components are subject to corrosion in certain treated timbers. The American Wood Preservers’ Association AWPA E17-99 standard test has been applied using mild steel, hot-dipped galvanised steel (HDG) and 316 stainless steel coupons to examine the feasibility of using aqueous media to model corrosion rates of fastener materials in contact with timber electrolytes. In order to achieve this, comparison has been made with previously published research dealing with corrosion rates in solid timber electrolytes. The results of the corrosion testing in aqueous copper-chrome-arsenate (CCA), copper azole (CuAz) and alkaline copper quaternary (ACQ) timber preservative solutions show that aqueous electrolytes cannot be used to accurately model the corrosion behaviour of mild steel and HDG mild steel timber fixing materials. In contrast to the results obtained in treated timber, HDG steel was found to be the most active material in terms of overall metallic losses during exposure to the aqueous solutions. In addition, CCA was considerably more aggressive than either the CuAz or the ACQ preservatives. The results are discussed in terms of electrolyte pH, metallic passivation and the thermodynamic behaviour of the anodic and cathodic reactions at the mixed (corrosion) potential.