b'CORROSION RESISTANCE CORROSIONRESISTANCE BY DOUG WELLSFASTENERS IN A COASTAL ENVIRONMENT Q uestionshavebeenposedexposure to a harsher surrounding envi- scale are more resistant than those lower aboutwhatcorrosionresis- ronment, such as salt-laden air, and mayonthechart.Magnesiumisthemost tance is required by Code orinclude dissimilar metal contact, exces- anodic,meaningitisthemostlikely by RCABC, and there is nosive building humidity, corrosive chemi- tocorrode,andthatothermetalswill straightforward answer. Corrosion resis- cals within components of the assembly,consume it. Most construction fasteners tance is required by BC Building Codeor corrosive elements provided withinare carbon steel wire (galvanized steel on 2018 and RCABC RoofStar Guaranteeor without of the building envelope, etc.the scale) which are then coated through StandardswithoutstatingwhatthatSo, while there are multiple factors tovarious means. A common coating for resistance is or providing a service lifeconsider, three stand out. roofing fasteners is zincvery low on the expectation.So,whatisacorrosionscale and intended as a sacrificial metal to resistant fastener? Factor 1: Metal Type protect the galvanized steel beneath.UnderstandingmetalcorrosionisElectrochemically dissimilar metals are critical:corrosionisadeteriorationofa common cause for corrosion in sheetFactor 2: Substratemetal caused by chemical reaction to itsmetal roofing materials. Metals that areAside from salt spray, fasteners some-surrounding environment. Corrosion canfarther apart on the galvanic scale willtimesaredrivenintopressure-treated beacceleratedviagalvanicreactionorcorrode faster, so metals higher on thewood (PTW). A common preservative www.rcabc.org l33'