A QUANTITATIVE WEATHERING STUDY OF WOOD SURFACES MODIFIED BY CHROMIUM-VI AND IRON-III COMPOUNDS .2. IMAGE-ANALYSIS OF CELL-WALL PIT MICRO-CHECKING

Radial longitudinal radiata pine wood surfaces were treated with dilute aqueous solutions of chromium trioxide, ferric chloride and ferric nitrate. Treated and untreated specimens were then exposed to natural weathering for 35 days. Scanning electron microscopy was used to obtain images of bordered and half bordered pits at treated and untreated surfaces before and after weathering. Images were converted to a digital form and the micro-checking and enlargement of pit apertures during weathering was then examined using image analysis. Application of chromium trioxide reduced the micro-checking and enlargement of both bordered and half bordered pit apertures during natural weathering. Both ferric treatments increased surface degradation. Image analysis of the micro-checking and enlargement of pit apertures at treated wood surfaces during natural weathering shows potential as a quantitative method of assessing the protective effect of chemical treatments, but measurement of the checking and enlargement of half bordered rather than bordered pit apertures may be preferable since checking of the former is more uniform.