AA-TR3-2004.pdf
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1、Minimizing er of Alum Copyright The Aluminum Association Inc. Provided by IHS under license with AA Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 04/18/2007 11:56:35 MDTNo reproduction or networking permitted without license from IHS -,-,- FOURTH EDITION, JANUARY 2004 I www.al
2、uminum.org The 2004, fourth edition has been revised through the support of the Technology Committee of the Sheet and Plate Division, ALUMINUM ASSOCIATION SHEET AND PLATE DIVISION COMPANIES Alcan Inc. Alcoa Inc. AMAG Rolling GmbH ARCO Aluminum, Inc. Coastal Aluminum Rolling Corus Aluminium Rolled Mi
3、lls, Inc. Products, USA Jupiter Aluminum Corporation Kaiser Aluminum and Chemical Corporation Logan Aluminum, Inc. Nichols Aluminum Ormet Corporation Pechiney Rolled Products Gulf Aluminium Rolling Mill United Aluminum Co. Corporation About The Aluminum Association The Aluminum Association, based in
4、 Washington, DC with offices in Detroit, MI, represents US. and foreign- based primary producers of aluminum, aluminum recyclers and producers of semi-fabricated products as well as suppliers to the industry. Member companies operate almost 200 plants in North America and many conduct business world
5、wide. NOTICE Disclaimer The use of any information contained herein by any member or nonmember of The Aluminum Association is entirely voluntary The Aluminum Association has used its best efforts in compiling the information contained in this book. While the Association believes that its compilation
6、 procedures are reliable, it does not warrant, either expressly or implied, the accuracy or completeness of this information. The Aluminum Association assumes no responsibility or liability for the use of the information herein. All Aluminum Association published standards, data, specifications and
7、other technical materials are reviewed and revised, reaffirmed or withdrawn. Users are advised to contact The Aluminum Association to ascertain whether the information in this publication has been superseded in the interim between publication and proposed use. The Incorporated Aluminum Association 9
8、00 19th Street, N.W., Washington, D.C. 20006 Copyright The Aluminum Association Inc. Provided by IHS under license with AA Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 04/18/2007 11:56:35 MDTNo reproduction or networking permitted without license from IHS -,-,- Guidelines for
9、 Minimizing Water Staining of Aluminum Contents 1 . Introduction . 4 2 . Causes of Water Stain 4 A.ExternalSources . 4 B . Moisture Condensation 4 3 . Packaging . 7 4 . Inspection Procedures 7 5 . Prevention . 8 6 . Conclusion 9 Appendices 1 . Aluminum Water Stain Prevention . 10 2.A. Measurement In
10、strument Suppliers . 1 0 2.B. Suppliers of Moisture indicating Labels . 10 2.C. Suppliers of Water Stain Preventatives 10 3 Copyright The Aluminum Association Inc. Provided by IHS under license with AA Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 04/18/2007 11:56:35 MDTNo rep
11、roduction or networking permitted without license from IHS -,-,- 1. Introduction but may cause processing problems where additional surface finishing or fabrication is to be performed. Virtually ail staining problems occur during shipping, handling, or storage. Some of the incorrect practices that r
12、esult in water staining and ways to minimize or avoid the staining are discussed in this pamphlet. A summary of the measures to minimize water staining is provided in Appendix 1 and is reproduced as a handy wall chart, which is included with this pamphlet. Copies of the chart may be obtained separat
13、ely from The Aluminum Association. Aluminum is naturally attractive and resistant to corrosion. Unlike most other metals, it takes care of itself. When exposed to dry or moist air it combines with oxygen to form a tough, transparent, protective oxide coating. In the presence of moisture, aluminum wi
14、ll not rust as will steel, but under certain conditions aluminum will stain. Such stains are usually found objectionable for esthetic reasons; they have no significant effect on strength 2. Causes of Water Stain Aluminum and other metals can stain when water is trapped between wraps, sheets or other
15、 mating surfaces. If there is no air flow to remove the water, prolonged contact between the water and the metal causes a reaction between the two which results in water stain. Figures 1 and 2 show examples of water staining on aluminum coiled and flat sheet, respectively. There are two main sources
16、 of this water: A. External Sources Obvious sources are rain, snow and water leaks. Water coming in contact with the surface of the aluminum from sources such as a leaking tarp on a truck or a leaking roof in a storage area has the potential for causing water stain. B. Moisture Condensation This is
17、the more complex of the two sources and therefore harder to understand and control. Air normally contains moisture in the form of invisible water vapor. Relative humidity, expressed as a percentage, provides a measure of the amount of water vapor actually in the air compared to the total amount of w
18、ater vapor that the air can hold. As the temperature of air increases, its capacity to hold water vapor increases. Dew point is the temperature at which water vapor from the air begins to condense and is affected by the relative humidity and temperature of the air. The dew point can be determined fr
19、om a chart (see Table i), based on simple measurements of air temperature and relative humidity. The type of instrument used to measure (and log) temperature and relative humidity is shown in Figure 3. The older style of thermometers containing mercury should not be used because mercury from broken
20、thermometers can corrode aluminum and other metals. Some suppliers of these instruments are listed in Appendix 2.A. Figure 1 - Water Stain on Coil Figure 2 - Water Stain on Sheet 4 Copyright The Aluminum Association Inc. Provided by IHS under license with AA Licensee=IHS Employees/1111111001, User=W
21、ing, Bernie Not for Resale, 04/18/2007 11:56:35 MDTNo reproduction or networking permitted without license from IHS -,-,- Figure 3 - Digital Instrument for Measuring Temperature this sets up the condition where water begins to condense on the surface of the aluminum. and spring months but may occur
22、whenever there are large enough fluctuations in temperature and humidity. Obviously this process is not limited to fall Figure 4 - Condensation on Cold Aluminum Cans During Loading: Loading metal removed from a cool or cold storage area into a warm trailer or railroad car, on a humid day, can result
23、 in condensation on the aluminum. This can occur during any season of the year; however, for some areas it may be more pronounced in summer. During Unloading-Moving Cold Metal Into Warm Storage: Condensation at the unloading point is more likely to occur during the cooler months. The following examp
24、le may help to clarify this point: Metal at 16C (60F) in a warehouse is loaded into a trailer and shipped. The metal is in transit for about two days. The outside temperature is - 1C (30F). Within a two-day transit period, the temperature of the metal gradually decreases to -1C (30F). When the alumi
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