Hydrogen embrittlement can cause your galvanized steel articles to fail prematurely. Learn what causes hydrogen embrittlement and what you can do to avoid it…
Working with galvanized steel brings with it lots of benefits AND lots of challenges. One such challenge is dealing with the problem of hydrogen embrittlement.
Hydrogen embrittlement is a type of deterioration process involving hydrogen atoms that remain trapped within the steel grains post production. These trapped hydrogen atoms, when they later try to escape, may cause the steel to crack – leaving it weak, damaged and at times completely unusable.
However, this problem is not common to all galvanized steel articles. It usually occurs in batches produced to tensile strength greater than 150 ksi.
Steel commonly absorbs hydrogen during the hot-dip galvanizing process, but most of these absorbed hydrogen atoms are expelled at the time when the plate is dipped into the galvanizing kettle.
This happens because of the kettle’s high temperature. In some cases though, the hydrogen atoms can remain trapped within the steel’s structure if the grain size of steel is too small. This usually happens in batches possessing high tensile strength (greater than 150 ksi); high tensile strength steels have small grain size.
So later, when the steel is bent or under load, these trapped hydrogen atoms become excited and they try to break free of their containments. In the process, they end up damaging the steel article, reducing its strength and ductility.
Of course as a fabricator or designer, you can’t do much about it; it’s a manufacturing defect not in your control. However, there’re still few things you can do to ensure that the stock of galvanized steel you’re buying is free of all such defects.
One solution is to make sure that you choose steel with a tensile strength less than 150 ksi. If a higher tensile strength steel is the requirement of your project, ask your supplier to modify their pickling process to produce a steel that is less susceptible to hydrogen embrittlement. Modified pickling reduces the amount of hydrogen the galvanized steel is exposed to, and gives you a product that is more robust and durable.
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