The Protection of Wood with Oxy-aluminium Compounds
F A Ximenes, P D Evans
Wood inorganic composites (WICs) containing aluminium compounds were developed and tested in relation to some essential requirements of preservative treated wood. Four different oxy-aluminium treatments were developed and identified according to the final insoluble compounds formed (sodium aluminate, aluminium hydroxide, magnesium aluminate and aluminium borate) in wood. Vacuum impregnation or double diffusion were used as delivery systems for the chemicals. Higher weight percent gains were obtained when wood was treated by vacuum impregnation. Inorganic deposits were detected throughout the structure of treated wood using scanning electron microscopy. A high degree of dimensional stability was imparted to Scots pine by the treatments, and significant dimensional stability was retained
even after treated wood was subjected to cold-water leaching. The oxy-aluminium treatments did not, however, impart water-repellency to wood. The decay resistance of oxy-aluminium treated wood, which was assessed through the use of terrestrial microcosms, was dependent on treatment, soil type and temperature, and exposure times. Oxy-aluminium treated wood showed increased resistance to brown rot. Sodium aluminate and aluminium hydroxide were more effective than magnesium aluminate and aluminium borate in protecting wood against soft rot. The results suggest that it is possible to protect some important wood properties with the use of oxy-aluminium compounds. Further research is needed to fully explore the potential of oxy-aluminium treatments for the protection of wood.