Zinc embrittlement is known as a kind of liquid metal embrittlement, a phenomenon where austenitic stainless steel and nickel alloy becomes brittle and/or cracks when it comes in contact with molten zinc. Zinc embrittlement can occur due to poor design and/or construction, but this study is focusing on the fire case.
In the fire case, galvanized steel is heated by flame, and when molten zinc drops on austenitic stainless steel, some plant owners believe the zinc embrittlement will occur. In order to prevent zinc embrittlement, some plant owners request shields to protect austenitic stainless steel piping and equipment that are located in close proximity to and, in particular, beneath galvanized steel structures, piping or equipment. However, it is not proven that a molten zinc drop can cause zinc embrittlement without the direct contact between galvanized steel and austenitic stainless steel.
In this study, laboratory tests and a pool fire simulation test were carried out to confirm whether zinc embrittlement occurs by fire without the direct contact between galvanized steel and austenitic stainless steel. As a result, it turned out that the risk of zinc embrittlement in fire case was very low without the direct contact of galvanized steel materials to austenitic stainless steel materials.
In the Flixborough Disaster, a chemical plant explosion in 1974 in the UK killed 28 people. The primary cause was inadequate repair work, and as a secondary cause, zinc embrittlement was observed at austenitic stainless steel piping.
As a lesson learned from this incident, some plant owners request to provide "Zinc Attack Protection" (ZAP) i.e., metal shield for stainless steel piping (examples are shown in Figure 1 and Figure 2), under galvanized steel piping or structures such as stairways/walkways to protect from molten zinc droplets in case of a fire. However, the source of zinc was not clear in Flixborough Disaster. Galvanized stairways/walkways or galvanized steel wire, which was used to secure the lagging box, were assumed to be the source, but the source has not been clearly identified.1 Galvanized steel wire might contact directly with the austenitic stainless steel piping or molten zinc might drop from melted galvanized stairways/walkways.2
