Leaching And Corrosive Character Of Copper Azole Wood Preservative

At a global level, wood preservatives based on copper, chromium and arsenic(CCA) hasprovided the core of water-based timber treatments during the last 70 years. The environmentalhealth hazards associated with the presence of arsenic and chromium have led to revisedformulation standards and codes of use in many countries. From December 2003, thepreservative-treated timber industry in the USA voluntarily removed ues of CCA forresidential applications. The United States Environmental Protection Agency (EPA) has nowbanned the use of CCA-treated wood in residential settings. The June 2004 amendment of theEuropean Union Commission Directive 76/769/EEC also states that arsenic compounds cannotbe used for the treatment of preservative-treated timber.The environmental friendly copper-based preservatives such as copper azole(CuAz)-basedproducts is one of the alternatives to CCA around the world. This study is major on seting up amethod for determination of propiconazole(PPZ) and tebconazole(TEB) in wood and intreating solutions by HPLC, leaching & recovery characteristics and corrosion of metal.The main research findings are summarized as follows:1) HPLC could be used for the determination of TEB alone or PPZ alone. The apparatus andreagents: ELITE P230 pump with 20μL loop injector; the column is a 200 mm C₁₈SinoChrom stainless steel column with an internal diameter of 4.6mm, filled with octadecylsilyl5μm packing; UV dector with a measuring wavelength of 220nm; EC2000 workstation;HPLC mobile phase is mix HPLC grade methanol and HPLC grade water in a 9:1 radio(v/v); the flow rate is kept constant at 1.0ml/min during the entire analysis; the retentiontimes are 4.1 min for TEB and 4.4min for PPZ.2) In most case of CuAz, the Copper fixation rate is higher than ACQ, but lower thanCCA-C. Of copper fixation rate of all CuAz, CuAz-7(Cu(OH)₂, NH3, PPZ) is highest,up to 99.6%, and the CuAz-9(Cu₂(OH)₂CO₃, EA, TEB) is lowest, that is 56.1%. Copperfixation rate of amine-based preservatives is less than ammonia-based ones. The fixationability in wood is Cu(OH)₂＞CuSO₄＞Cu₂(OH)₂CO₃.3) TEB & PPZ leaching rate is very low. Of all CuAz CuAz-2 (CuSO₄-5H₂O, EA, TEB), CuAz-6 (Cu(OH)₂, EA, TEB) and CuAz-8 (Cu(OH)₂, EA, PPZ) are mostly leaching,the others are still very high, more than 95%.4) Of TEB & PPZ recycle rate of all CuAz, CuAz-3 (CuSO₄-SH₂O, NH₃, PPZ) is highest,up to 98.4%, CuAz-1 (CuSO₄-SH₂O, NH₃, TEB),CuAz-4 (CuSO₄-SH₂O, EA, PPZ),CuAz-7 (Cu(OH)₂, NH₃, PPZ) and CuAz-8 (Cu(OH)₂, EA, PPZ) are lower than 50%,the others are higher than 60%.5) CCA is less corrosive to red brass and Q235A steel than other copper formulations;Copper-based preservatives such as ACQ and copper azole derived from basic cupriccarbonate or cupric hydroxide are less corrosive to Q235A steel than these from cupricsulfate; Ethanolamine is less corrosive to Q235A steel than ammonia in ACQ derived fromcupric hydroxide, while other ingredients are same; The 304L stainless steel performedwithout significant corrosion loses in all of the preservative treatments examined; andEpoxy resin coating could be used for protecting red brass, Q235A steel as well as zin hotgalvanized steel from preservative corrosion.