先说结论：

G550AZ150的钢带，全世界最好，最大，知名度最高的生产商bluescope，承担法律责任的承诺是：在离海边100米以上，全部包覆非暴露的条件下，按规范施工……等条件下，50年。

Summary of a ten year report produced by NAHB Research Center, a subsidiary of the National Association of Home Builders (NAHB) in the US and sponsored by International Zinc Association

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 Buildings was a study commissioned by the International Zinc Association (IZA) that measured actual zinc and zinc-alloy coating corrosion rates of steel framing samples in four different home environments in the US and Canada over a ten year period. The NAHB 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10年期TEN YEAR PERIOD关于镀锌和镀锌合金腐蚀的研究

INTRODUCTION 

This summary report is based on the corrosion data presented in the NAHB Research Center’s ten year sample retrieval report, January, 2009. The test sites were in Miami, Florida; Leonardtown, Maryland; and Long Beach Island, New Jersey in the US; and Hamilton, Ontario in Canada. At each site, numerous test samples were installed inside and in some cases, outside of the building (e.g.; roof trusses, floor systems, walls, decks). The ten year coating loss measurements from the four sites have shown minor mass losses for all coating types in all sample colonies (e.g., walls, attics, floor joists). While calculating life expectancies based on the very low coating weight losses found in this study is inexact, the measured coating corrosion rates extrapolate to coating life predictions of 300 to over 1000 years in wall, floor, and roof framing. Sample colonies intentionally located in more aggressive exposures, suchas underneath an outdoor deck and in an exposed crawl space located next to aggressive tidal waters, exhibited higher corrosion rates, but still had a coating life greater than 150 years. Steel is not recommended for outdoor use such as under decks. For an area near the coast or other aggressive bodies of water, steel in a vented or exposed crawl space would be specified with a heavier coating to significantly extend its life.

本总结报告基于NAHB研究中心2009年1月发布的十年样品检索报告中的腐蚀数据。测试地点在佛罗里达州的迈阿密;马里兰州Leonardtown;美国新泽西州长滩岛;还有加拿大安大略省的汉密尔顿。在每个工地，都安装了大量的测试样本，有的安装在建筑物内，有的则安装在建筑物外(例如;屋顶桁架，地板系统，墙壁，甲板)。从四个地点进行的十年涂层损失测量显示，所有样品菌落(如墙壁、阁楼、楼板搁栅)的所有涂层类型的质量损失都很小。虽然基于本研究中发现的极低涂层重量损失计算预期寿命是不准确的，但测量到的涂层腐蚀速率可以推断出涂层在墙壁、地板和屋顶框架中的寿命预测在300年到1000年以上。有意将样本置于更强的暴露环境中，如户外甲板下和靠近强潮汐水域的暴露的爬行空间中，显示出更高的腐蚀速率，但涂层的使用寿命仍大于150年。钢不推荐用于户外使用，如甲板下。对于靠近海岸或其他侵蚀水体的区域，在通风或暴露的爬行空间内的钢材应指定较重的涂层，以显著延长其使用寿命。

CONCLUSION 

Coating corrosion was minimal from all four sites, for all sample types (studs and plates), all sample coatings (galvanize, Galvalume®, and Galfan®), and all sample colonies (e.g., crawl spaces, walls, attics, joists). Lower corrosion rates were found with samples installed in wall cavities and attics where the environments were more controlled with less exposure to humid conditions. Higher coating corrosion rates were found in locations with exposures to higher levels of humidity and outdoor pollutants, such as with samples installed in the floor above the carport of the New Jersey site or samples located in the crawl space of the Leonardtown site.For enclosed locations (walls, attics, floors) the extrapolated coating life predictions ranged from 300 to over 1000 years. For exterior exposures or semi-exposed locations in an aggressive environment subject to higher humidity and exterior pollutants, thehigher corrosion rates still extrapolated to over 150 years of coating life.The life span of the zinc and zinc-alloy coated steel samples studied in this project was found tobe well beyond the life expectancies of modern buildings. The results of this study agree with the results from a similar study conducted by Corus Research in the United Kingdom.

对于所有样品类型(螺柱和板)、所有样品涂层(镀锌、Galvalume和Galfan)以及所有样品(例如爬行空间、墙壁、阁楼、搁栅)，所有四个位置的涂层腐蚀都很小。将样品安装在壁龛和阁楼中，可以发现腐蚀速率较低，因为壁龛和阁楼的环境控制较好，接触的潮湿条件较少。暴露在较高湿度和室外污染物环境中的地点，如新泽西州场地车库上方的地板上安装了样品，或莱昂纳德敦场地的爬行空间中安装了样品，发现涂层腐蚀率较高。对于封闭的位置(墙壁、阁楼、地板)，外推的涂层寿命预测范围从300年到1000年以上。对于外部暴露或半暴露的位置，在一个侵略性的环境中受到较高的湿度和外部污染物，较高的腐蚀率仍然推断出超过150年的涂层寿命。本工程研究的锌及锌合金涂层钢试样的使用寿命远远超过现代建筑的使用寿命。本研究的结果与Corus Research在英国进行的一项类似研究的结果一致。

补充资料 

以上毕竟是试验或者研究数据，真正到了商业应用层面，在国外一般以warranty的形式，由产品制造商对产品的使用年限进行保障，为了降低风险，所有warranty都有对应的“免责条款”，研究这种免责条款，是正确应用该产品的一个有效手段。

以澳大利亚bluescope zinalum为例，详细介绍一下厂家愿意承担的质保年限和对应的免责条款。

首先登陆https://warranties.bluescopesteel.com.au

假设我们是澳洲某房屋的业主，我们选择如下：

右侧可以选择产品系列，选择truecore产品，就是淡淡的蓝色那种钢带，如G550AZ150,下方有个滑动条，代表距离海边（或者污染源）的距离，选择100米（注意：100米内是无法选择的，也就是100米内bluescope不提供质保），右侧圆形图案有三个选项，分别是：

Surf: Area exposed to breaking surf and ocean spray

Exposed: Open expanses of salt or brackish water exposed to onshore winds, but not typically prone to breaking surf

Calm: Protected areas of salt or brackish water, including ports, harbours, bays, and river estuaries

选择calm这种正常环境，给出的结论是主结构最高50年，局部最高25年……如果感兴趣，自己可以尝试各种组合。

最后，给出一个warranty的范本，最后唠叨一句，任何没有条件的承诺都是耍流氓……