CORROSION OF MILD STEEL, HDG STEEL AND 316 STAINLESS STEEL IN CCA, CuAz AND ACQ TREATED PINUS RADIATA

摘要

BRANZ, as an independent testing laboratory to the building industry, has developed an EmbeddedrnFastener Test for the measurement of metallic corrosion rates in treated timbers. In this work, thernperformance of this embedded fastener methodology has been compared with the American WoodrnPreservers' Association (AWPA) standard E12-94 test, which uses the corrosion analysis ofrnmetallic coupons 'sandwiched' between two timber blocks. The testing focused on the CCArnalternatives ACQ and CuAz timber preservative treatments. AWPA E12-94 mild steel corrosionrnrates in the ACQ treated timber have been shown to increase by a factor of up to five at the H3.2rnhazard level relative to the equivalent CCA treated timber. 316 stainless steel performed very wellrnfor all of the preservative treatments examined. The relative magnitude of corrosion rates measuredrnusing the Embedded Fastener Test contrasted significantly with those determined using the AWPArnstandard methodology. Using commercially available mild steel and hot-dipped galvanised nails,rnthe ACQ treated timber produced corrosion rates ranging from one and a half to two times that ofrnthe equivalent H3.2 CCA treated samples. It is concluded that the AWPA standard test increasesrnthe differentiation of mild steel corrosion rate between timber treatment types, but the relativernmagnitude of acceleration cannot be directly compared to that experienced by fasteners embeddedrnin the same timbers.