Effects of Climate on Exterior Wood Coating Performance: A Comparison of Three Industrial Coatings in a Warm-Summer Mediterranean and a Semi-Arid Climate in Oregon, USA

Wood exposed in exterior applications degrades and changes color due to weathering and fungal growth. Wood coatings can reduce the effects of weathering by reducing the damaging effects of ultraviolet light, reducing water absorption, and slowing fungal growth on the surface. Coating performance depends on the blend of resins, oils, and pigments and varies considerably among different wood species and conditions. Specific information describing expected service for different wood species and exposure conditions is not commonly available; certain combinations may work well in one climate or on one timber species, but underperform elsewhere. This study compared the performance of three industrial wood coatings on two wood species for two temperate climates under natural weathering conditions. Most of the coatings/species combinations lost their protective properties within 12 to 15 months; however, fungal growth was more prevalent at the wetter site than at the drier site for several combinations. Film-forming coatings often peeled and cracked, while penetrating coatings weathered and changed color relatively uniformly during the study. While no coating was completely effective, the results illustrate the benefits of using coatings that promote the development of natural, uniform-patinaed wood surfaces. The findings also guide coating maintenance programs for mass timber structures exposed to natural weathering conditions.

Practical and Thermodynamic Constraints on Electromicrobially-Accelerated CO2 Mineralization

By the end of the century tens of gigatonnes of CO2 will need to be removed from the atmosphere every year to maintain global temperatures. Natural weathering of ultramafic rocks and subsequent mineralization reactions can convert atmospheric CO2 into ultra-stable carbonates. But, while natural weathering will eventually draw down all excess CO2, this process will need hundreds of thousands of years to do it. The CO2 mineralization process could be accelerated by weathering ultramafic rocks with biodegradable lixiviants like organic acids. But, in this article we show that if these lixiviants are produced from cellulosic biomass, the demand created by CO2 mineralization could monopolize the world's supply of biomass even if CO2 mineralization performance is high. In this article we demonstrate that electromicrobial production technologies that (EMP) combine renewable electricity and microbial metabolism could produce lixiviants for as little as $200 to $400 per tonne at solar electricity prices achievable within the decade. Furthermore, this allows the lixiviants needed to sequester a tonne of CO2 to produced for less than $100, even with modest CO2 mineralization performance.

A durable coating to prevent stress corrosion effects on the surface strength of annealed glass

The durability of an innovative polymeric coating recently developed by the authors to prevent stress corrosion in annealed glass is herein examined. The coating, having functional graded properties through the thickness, is optimised to provide a very good adhesion with glass and an excellent hydrophobic behavior on the side exposed to the environment, thus creating a good barrier to humidity, which is the triggering agent for stress corrosion. Three scenarios are analysed in terms of ageing: (i) cyclic loading, accomplished by subjecting coated samples to repetitive loading; (ii) natural weathering, performed by exposing coated samples to atmospheric agents; (iii) artificial weathering, carried out by exposing coated specimens to fluorescent UV lamps, heat and water. The durability of the coating is assessed indirectly, on the base of its residual effectiveness in preventing stress corrosion, by comparing the bending strength, obtained with the coaxial double ring test, of aged coated glass specimens with that of un-coated and freshly coated specimens. The obtained results prove that the proposed formulation is almost insensitive to cyclic loading, maintains a very good performance in case of natural weathering, whereas is slightly more sensitive to artificial weathering.

Graffiti Protection on Concrete in the New Building and in the Renovation

With the increase of graffiti since the beginning of the 1970s, the interest in proper removal and high-quality protection systems also have grown. To protect affected objects and buildings from damage caused by graffiti, anti-graffiti systems (AGS) can be used. In practice, it has already been shown that no AGS is suitable for all kind of surfaces. In this study, the effects of permanent anti-graffiti systems on various concrete surfaces are specifically investigated and evaluated with test series under natural weathering (over 3 years). The focus is put on functionality (visual influences) and durability (surface properties of the concrete).

Surface Protection of Wood with Metal Acetylacetonates

Metal acetylacetonates are coordination complexes of metal ions and the acetylacetonate anion with diverse uses including catalysts, cross-linking agents and adhesion promotors. Some metal acetylacetonates can photostabilize polymers whereas others are photocatalysts. We hypothesize that the ability of metal acetylacetonates to photostabilize wood will vary depending on the metal in the coordination complex. We test this hypothesis by treating yellow cedar veneers with different acetylacetonates (Co, Cr, Fe, Mn, Ni, and Ti), exposing veneers to natural weathering in Australia, and measuring changes in properties of treated veneers. The most effective treatments were also tested on yellow cedar panels exposed to the weather in Vancouver, Canada. Nickel, manganese, and titanium acetylacetonates were able to restrict weight and tensile strength losses and delignification of wood veneers during natural weathering. Titanium acetylacetonate was as effective as a reactive UV absorber at reducing the greying of panels exposed to 6 months of natural weathering, and both titanium and manganese acetylacetonates reduced the photo-discoloration of panels finished with a polyurethane coating. We conclude that the effectiveness of metal acetylacetonates at photostabilizing wood varies depending on the metal in the coordination complex, and titanium and manganese acetylacetonate show promise as photoprotective primers for wood.