Application of copper monoethanolamine solutions as primers for semitransparent exterior wood stains

The effects of copper monoethanolamine (CuA) treatment of wood surfaces on the surface weathering and durability of a semitransparent penetrating stain were compared with those of chromic acid (CrA) treatment which is known as a photoprotective primer, using artificial weathering trials. Chemical changes in chemically treated and untreated wood surfaces during artificial weathering were investigated using Fourier transform infrared (FTIR) spectroscopy. Surface roughness, water contact angle measurements and scanning electron microscopy observations were performed to assess stain durability. Results of FTIR analyses indicated that lignin losses following CuA and CrA treatment were less than those of the untreated wood surfaces during the initial stage of artificial weathering. CuA pretreatment prior to staining also retarded the increase in the average surface roughness compared with that observed for the CrA-pretreated surface and untreated control (only stained) during artificial weathering. Furthermore, CuA pretreatment retarded the decrease in the contact angle compared with that observed for the untreated control, although the use of a highly concentrated CuA solution led to a decrease in the water repellency of the stained wood surface. These results indicated that CuA solution could be used for the pretreatment of wood surfaces to enhance the durability of semitransparent penetrating stains, as long as excessive CuA concentrations are avoided.