镀锌（镀铝锌）冷弯薄板型钢的耐久性（能用多少年？）

Summary of aten year reportproduced by NAHBResearch Center,a subsidiaryof the NationalAssociation ofHome Builders(NAHB) in the USand sponsored byInternational ZincAssociation

全美住宅建造商协会（NAHB）

是美国最大的非盈利性、非政府的行业协会，它由住宅建造商以及与住宅建造业直接有关的技术开发和产品生产企业组成。全美住宅建造商协会迄今已有65年历史，在美国和世界其他将近50个国家拥有203,000个会员，通过全美住宅中心和总数超过850个的附属机构及各州和地方协会，为会员提供广泛的服务。

赞助商是国际镀锌业协会

OVERVIEW

Durability of Galvanized Steel Framing in Residential Buildingswas a study commissioned by the International Zinc Association(IZA) that measured actual zinc and zinc-alloy coatingcorrosion rates of steel framing samples in four different homeenvironments in the US and Canada over a ten year period. TheNAHB Research Center was the research contractor

说是NAHB承包了这项研究，在美国和加拿大进行了一个TEN YEAR PERIOD关于镀锌和镀锌合金腐蚀的研究

INTRODUCTION

This summary report isbased on the corrosiondata presented in theNAHB Research Center’sten year sample retrievalreport, January, 2009.The test sites were inMiami, Florida; Leonardtown,Maryland; and LongBeach Island, New Jerseyin the US; and Hamilton,Ontario in Canada. At eachsite, numerous test sampleswere installed insideand in some cases, outsideof the building (e.g.;roof trusses, floor systems,walls, decks).The ten year coating lossmeasurements from thefour sites have shownminor mass losses for allcoating types in all samplecolonies (e.g., walls, attics,floor joists). While calculatinglife expectancies basedon the very low coatingweight losses found inthis study is inexact, themeasured coating corrosionrates extrapolate tocoating life predictions of300 to over 1000 years inwall, floor, and roof framing.Sample colonies intentionallylocated in moreaggressive exposures, suchas underneath an outdoordeck and in an exposedcrawl space located nextto aggressive tidal waters,exhibited higher corrosionrates, but still had a coatinglife greater than 150years. Steel is not recommendedfor outdoor usesuch as under decks. Foran area near the coast orother aggressive bodies ofwater, steel in a vented orexposed crawl space wouldbe specified with a heaviercoating to significantlyextend its life.

CONCLUSION

Coating corrosion wasminimal from all four sites,for all sample types (studsand plates), all samplecoatings (galvanize,Galvalume®, and Galfan®),and all sample colonies(e.g., crawl spaces, walls,attics, joists).Lower corrosion rateswere found with samplesinstalled in wall cavitiesand attics where theenvironments weremore controlled withless exposure to humidconditions. Higher coatingcorrosion rates were foundin locations with exposuresto higher levels of humidityand outdoor pollutants,such as with samplesinstalled in the floor abovethe carport of the NewJersey site or sampleslocated in the crawl spaceof the Leonardtown site.For enclosed locations(walls, attics, floors) the extrapolated coating lifepredictions ranged from300 to over 1000 years.For exterior exposures orsemi-exposed locations inan aggressive environmentsubject to higher humidityand exterior pollutants, thehigher corrosion rates stillextrapolated to over 150years of coating life.The life span of the zincand zinc-alloy coatedsteel samples studied inthis project was found tobe well beyond the lifeexpectancies of modernbuildings. The resultsof this study agree withthe results from a similarstudy conducted by CorusResearch in the UnitedKingdom.

说是封闭环境300-1000年，开口，有污染环境150年。你信吗？不信可以打个折，5折可行？