This is de-lamination. It is the galvanizing layer peeling off the steel. It is caused by excessively thick coatings that grow due to high silicon levels in steel. If treated carefully this type of steel can be successfully galvanized and will provide longer lasting protection. The coating is more brittle and prone to abrasive damage. This cannot be controlled by the galvanizer and can be avoided by using steels that fall outside the Sandelin range (range of silicon levels that generate more rapid and un-checked alloy crystal growth.) This needs to be repaired and responsiblity for this repair agreed between the parties.

grey, peeling, flaking

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