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11044 Evaluation of High Temperature Cracking Risk of Stainless Steels in Presence of Zinc Silicate

Product Number: 51300-11044-SG
ISBN: 2011 11044 CP
Author: Matina THAMMACHART, Yves GUNALTUN, Suchada PUNPRUK and Siriporn DAOPISET
Publication Date: 2011
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The zinc-containing primers, especially zinc silicate, are widely used on the carbon steel for both onshore and offshore environments. Their use on stainless steels is not recommended since there is a risk of liquid metal embrittlement by molten zinc in case of fire due to its low melting point. Zinc silicate contains metallic zinc particles which can diffuse into the stainless steel if the particles melt. However, zinc quantity may not be sufficient (the thickness is 60 to 90 microns) to initiate a significant cracking. Also the oxidation of zinc particles, which are very small, before they reach melting temperature, would not permit cracking of stainless steels. In order to confirm these possibilities some tests were carried out on three types of stainless steels painted with 60 to 90 microns of zinc silicate and heated to temperatures 400 to 650oC. No cracking was observed on painted samples but cracking was experienced on stainless steel samples when a piece of zinc is placed on the stainless steel surface. This paper summarizes the test results and discusses the possible reasons of non-cracking.

Key words: liquid metal embrittlement, zinc silicate, stainless steel.
The zinc-containing primers, especially zinc silicate, are widely used on the carbon steel for both onshore and offshore environments. Their use on stainless steels is not recommended since there is a risk of liquid metal embrittlement by molten zinc in case of fire due to its low melting point. Zinc silicate contains metallic zinc particles which can diffuse into the stainless steel if the particles melt. However, zinc quantity may not be sufficient (the thickness is 60 to 90 microns) to initiate a significant cracking. Also the oxidation of zinc particles, which are very small, before they reach melting temperature, would not permit cracking of stainless steels. In order to confirm these possibilities some tests were carried out on three types of stainless steels painted with 60 to 90 microns of zinc silicate and heated to temperatures 400 to 650oC. No cracking was observed on painted samples but cracking was experienced on stainless steel samples when a piece of zinc is placed on the stainless steel surface. This paper summarizes the test results and discusses the possible reasons of non-cracking.

Key words: liquid metal embrittlement, zinc silicate, stainless steel.
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