Tag Archives: Zincalume

Steel Siding Failure?

In my fledgling days in the pole building industry, we jumped on board when ASC Pacific began offering “Twice the Life” Zincalume® coated steel roofing panels as an alternative to bare galvanized. Keep in mind, back in the early 1980’s almost every roof was unpainted – so this was huge!

One side benefit of Zincalume® is the aluminum content of the protective coating causes the bare panels to oxidize to a milky white over time, unlike the red rust of galvanization. One prolific Pacific Northwest builder even sold Zincalume® to customers telling them they would eventually have a white roof!

My business had provided a three sided “machine shed” 40 foot deep by 60 feet long and 10 foot eave to a farmer in the state of Washington. Within a year after he had the building up, he called because he had fist sized holes in the roof of his barn!

Well, there was a “Paul Harvey” to his story….he had enclosed the open side of the building, and then used it for raising hogs! The building had absolutely no ventilation provisions, nor was there a vapor barrier installed under the roof steel.

The wastes produced by the hogs contained a very high amount of ammonia, which reacted with the aluminum in the Zincalume®, and literally ate holes in it!

rusted steel sidingWe recently had a client send us the photos seen with this article. Their four year old building had developed a series of rust through holes and the client wanted to know if the steel panels were still under warranty.

Strangely, the holes are all in a straight line, across one panel of steel and just onto the next panel. The line of holes just happens to coincide with the location of a “bookshelf” style wall girt on the inside of the building. Nowhere else on the building is there any sign of rust.

While the ultimate authority will be the steel roll forming company, my suspicion is some corrosive material was placed on the bookshelf girt (which was being used as a shelf), and it leaked or spilled along the girt line.

What came to mind first was an old battery. A frequent poster to internet discussion boards, from Tennessee, had this to say about battery acid and steel:

“I fought the battery acid contamination for years on mine equipment on metal a heck of a lot thicker…” “What I found is no amount of rinsing, or pressure washing will stop the damage from continuing and once the metal is contaminated replacement is about the best solution. The problem with acid is not just having the corrosive substance lying on the surface dissolving the metal, but the fact that once contaminated a chemical reaction is started that is very hard to stop! The acid will “eat” into the metal and cannot be simply rinsed off nor is it easy to neutralize for the same reason.”

Steel roofing and sidings are strong and affordable, however care must be taken to protect them from caustic situation, which may lead to premature failure of the product.

Galvalume ®

Galvalume SteelMy first exposure to Galvalume ® was when ASC Pacific introduced “twice-the-life” Zincalume in the 1980s. They were marketing the product in its bare (unpainted) form as an alternative to the more familiar bare galvanized sheet steel. It looks similar to galvanized steel, but the visible crystals (or spangle) are smaller and close together, giving it a smoother appearance.  The combination of zinc and aluminum enhances both the positive and negative effects of aluminum.

Because aluminum is corrosion-resistant, Galvalume is more corrosion-resistant than galvanized steel, but because aluminum provides barrier protection instead of galvanic protection, scratches and cut edges are less protected.
Most consumers are familiar with old barn with bare galvanized steel panels which rusts (oxidizes) red. Bare Galvalume steel panels are not bright and shiny when new, unlike galvanized panels. As Galvalume ages, it oxidizes white. One prolific builder in the Pacific Northwest was actually even selling the product as a white roof!

Galvalume is a sheet steel with a hot dip applied alloy coating of about 55% aluminum 45% zinc. It is manufactured and sold as a trademarked product by companies such as Bethlehem Steel and National Steel.

I did find out, (the hard way) there are some limitations to uses of bare Galvalume steel panels. When the product first came on the market, we provided it as roofing for a building which later became a hog confinement barn (unbeknownst to us). The client called within two years of the roofing being installed, to complain about fist sized holes developing in his roofing. According to the roll former, It turns out the Galvalume coating had a chemical reaction to the confined urea, which basically “ate” holes in the steel. For this reason, Galvalume is best not used in animal confinement buildings.

Prepainted Galvalume roofing and siding panels are now used on buildings everywhere. It combines well with most other building materials and treatments. As such its versatility allows it to be used almost anywhere on building exteriors. Its excellent corrosion resistance has been proven by field performance on buildings for decades. An estimated 40 billion square feet of prepainted Galvalume sheeting covers buildings in all kinds of climates and environments in North America, Europe, Asia and Australia. The combination of long-lived Galvalume sheet with a wide range of modern high-performance paint systems results in a functional, durable, eye-appealing building product.