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Aside from catastrophic damage, metallic corrosion is clearly the chief cause of metal building panel failure.  When architectural metal panels corrode, there are undesirable consequences that go beyond cosmetics.  Corroding panel systems will begin to leak, causing potentially significant damage to the interior of a building.  Repair costs can be substantial, usually involving removal and replacement.

Contrarian Metal Resources was founded on a philosophy of designing for performance, using corrosion resistant metals.  We supply high performance metals that, when properly specified and installed, will last the useful life of a building with little or no maintenance.

GALVANIZED STEEL

Testing of galvanized steel at Kure Beach in North Carolina showed .68 mils per year of loss after 13 years of marine exposure (reference Table 13 in the attached excerpt from the Nickel Development Institute (NIDI) Reference Book 11 024).  Information in Table 14 of the same reference suggests a useful life of bare galvanized at 5-15 years in a rural, low pollution environment.

ALUMINUM

As in the case of galvanized, painting or anodizing aluminum will greatly enhance its useful life.  The appearance of the paint finish will be roughly the same as galvanized.  Anodizing also adds protection from the elements, but consistency of appearance from panel to panel is difficult to achieve.

The NIDI tables indicate bare aluminum will corrode at a rate approaching .07 mils per year in an inland environment.  Further, bare aluminum will oxidize, which may not be desirable from a cosmetic standpoint.                                                                                       Illustration 1

We would suggest that like galvanized, painted aluminum will look good for 10-25 years.  However, it will remain serviceable for a matter of decades after the appearance has deteriorated.  This is also true of bare aluminum, if a chalky oxide surface (that will develop) is acceptable.  However, in a marine environment, significant deterioration can occur.  The photograph in Illustration 1 was taken in Tampa, Florida in 2002.  The painted aluminum panels installed in 1982, were corroded to the point of failure in less than 20 years.

STAINLESS STEEL

The results of field tests on stainless steel outlined in the NIDI tables suggest negligible metal thickness loss to corrosion.  Further, stainless steel maintains its original appearance through its natural passive film layer of "invisible" chromium oxide.  The only maintenance normally required is to keep gutters free of debris and wash the building periodically (often many years apart) to maintain a good appearance.

The more highly engineered stainless steel finish treatments offered by our company provide excellent consistency of appearance without any coatings to deteriorate.  When the proper grade is selected, our products are covered by a 30-year Contrarian Metal Resources warranty (please refer to grade selection and product data sheets in the PRODUCTS section).  We would expect the useful life to actually be some number of decades beyond that.  Stainless steel building panels have existed for as long as 70 years (Chrysler & Empire State Buildings, for example), maintaining a good appearance without failure.  There are no known stainless buildings constructed prior to the late 1920's.  In short, count on stainless steel existing with little maintenance for the useful life of the building.

The photographs in Illustration 2 below were taken a year ago at the LaQue Laboratories test site at Kure Beach, NC.  The metal coupons were installed 820 feet from mean high tide for the duration noted:

Painted Cast Aluminum	Type 304 Stainless	Type 316 Stainless
12 Years	59 Years	59 Years

TITANIUM

Although it is considerably more expensive than stainless steel, titanium provides the best value in severely corrosive environments.  In almost any location, it will perform for decades.  It has a somewhat duller surface aspect than stainless steel.  It is also inherently more variable in appearance.  However, the special processing of our InvariTech^TM and InvariSand^TM finishes provides good consistency of appearance.   Titanium is at home in severe seacoast environments where salt spray can be expected to dry on the building panel surfaces.  Even Type 316 stainless will deteriorate under these conditions.  Our Titanium bears a 30 year limited warranty (please refer to product data sheets in the PRODUCTS section).  For more information about titanium properties, you will find RMI Titanium's website to be quite helpful.

ZINC

Heavy gauge zinc roofing panels have existed for more than a century in Europe without failure.  Although the NIDI tables suggest improved performance in a marine environment compared to some metals, there is a degree of erosion corrosion that must be anticipated in coastal areas.

Zinc panel systems must be back ventilated in order to prevent corrosion from the interior surfaces propagated by trapped moisture.  Our InvariTique With Back Coat^TM has a coil coating on the back side that eliminates the need for traditional zinc ventilation requirements.  Warranties for our zinc products are available on a specific project basis, upon our assessment of the environment and design review.  More about the ventilation requirements of ZINC can be found in the INFORMATION TOPICS section.  For additional information regarding the properties of zinc, Alltrista Zinc Products is an excellent resource.

Aside from erosion corrosion of metals in given environments, there are also fabrication and installation issues that can affect performance.  Architectural metal panel systems that do not drain well can promote galvanic and crevice corrosion, for example.  We offer some basic rules to follow when designing with metals:

• Provide sufficient drainage so as not to allow water to collect on metal surfaces
• Separate dissimilar metals with plastic washers or other means
• Provide a degree of back ventilation to prevent moisture from being trapped on the interior surfaces of the panels
• Remove heat tint (from welding) from the surface of the metal through chemical or mechanical means
• Advise owners to periodically wash the panels and keep gutters clear of debris

Following these guidelines will increase the life span of your panel system.
If there is any doubt about selecting the best material for your project, please contact us .  Our metallurgical engineers are available to provide assistance.  We can also provide material cost estimates of different options to help you evaluate the lowest cost material in the long run.