Failure Analysis On Corrosion of Al-Zn Heat Reflector in Timber Dry Kiln

Abstract

Al-Zn alloy coated steel sheet (JIS G3 141) was used as a heat reflector in timber dry kiln. After six months continuous service at 110 derajat celcius in moist condition, the heat reflector is corroded. Failure analysis method was used to analyze this corrosion phenomena. Macroscopic and microscopic examination with some characterizations have been performed to determine the elemental composition and corrosion products. The elemental composition of corroded heat reflector that were detected by SEM-EDS are sulphur, chloride, calcium, sodium and potassium. XRD analysis revealed the zinc aluminum carbonate hydroxide hydrate (Zn6Al2(OH)16CO3.4H2O) black rust staining and iron oxide (FeFe204), as corrosion product. Environmental condition in timber dry kiln with the existence of acid and alkaline elements make the corrosion process occur. Those elements came from the dried timber and steam that adhered on the heat reflector surface and they attacked the Al-Zn coating and base metal. The humidity and high temperature in timber dry kiln environment are factors that increase the corrosion rate of the heat reflector.