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Question 1828268 640

From time to time, our members call the AGA with stories describing issues we have never heard of before. Often we are tasked to assist our members in finding a solution or speaking with industry experts to lend their opinion. In an effort to pass along what we learned from our members, I wanted to share the results from two recent investigations.

A galvanizer recently contacted the AGA regarding a skyscraper project in Manhattan, NY where a hot-dip galvanized coating inspection was performed above the 60th floor during ongoing construction. Upon climbing to the various floors requiring inspection, the galvanizer found all the digital coating thickness inspection gauges were completely unresponsive once at the elevated job site. To learn why this may occur on other jobs sites and how to avoid this issue in the future, see what the galvanizer and I learned upon contacting the gauge manufacturer:

Electromagnetic Interference with Corded Inspection Probes

Meanwhile, several galvanizers in the Pacific Northwest area of the United States contacted the AGA regarding a surface condition which presented itself as sharp, raised spikes after hot-dip galvanizing. This condition was unable to be identified prior to galvanizing, and was mostly found on hot-formed, semi-finished products, including flat bar, round/square stock, angle and channel. At first, we believed the condition to be a localized dross issue, but this proved an incorrect evaluation. An investigation revealed the presence of steel laps from steel manufacturing may be the root cause, but many attempts to identify and remedy the surface prior to galvanizing have been unsuccessful. As a result, discussions with steel manufacturers in the area are ongoing. For more information on this issue and what is being done about it:

Rough Surface Condition Due to Steel Laps

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Barry Dugan

I worked on a similar problem years ago. It was hog-flooring that had a pimple problem. It was so bad, that it was ripping the underside of the hogs. Of course, the manufacturer was blaming the galvanizer. The cage floor was made of tri-bar (3-sided bar, about 3/8"). I don't know if the bar was cold-drawn, or hot-drawn, but it left numerous little laps in the steel surface. You could not see them prior to galvanizing. But the heat of galvanizing would cause the lap to raise slightly, allowing the molten zinc to seep beneath the lap. These pimples were needle sharp. These needles could only be confirmed with a photo of the metallographic cross section.

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