In the energy industry, there are many steel components that must withstand the elements at their harshest extremes in Australia, and millions of dollars are spent on ensuring they don’t cause a catastrophic failure. Often, this can require highly expensive materials, rigorous maintenance regimes, numerous repairs or replacements.
Hydrogen embrittlement is one of the many concerns that the industry has tried to address since it was identified in 1875 by W.H. Johnson. Hydrogen embrittlement is the permanent loss of ductility of a metal, which is caused by the presence of hydrogen in combination with stress.
The result is intergranular fractures through the grains of steel. This hydrogen often arises in a manufacturing process, where the pickling of steel is involved in the galvanising or electroplating process.
It can also arise in situations in the right (wrong) environmental conditions, which can include salinity of water or air vapour, leachates, effluent, or acidity of rainwater.
It is caused by the absorption of hydrogen atoms into the steel, with trapped ‘H’ atoms subsequently forming ‘H2’ gas molecules within the steel, resulting in extreme internal stresses. It is the combination of material susceptibility through its properties, the stress load under which it is performing, the hydrogen source in production, and the environment which leads to potentially disastrous failures.
Of course, we still need to provide very robust corrosion protection to ferrous parts to avoid the expensive maintenance and replacement programs in future years or use highly expensive non- corrosive materials.
Coatings that produce a lot of hydrogen in their processes, such as electroplating and hot-dip galvanising, should be avoided. A coating that allows the product to be baked in ovens to allow the diffusion of hydrogen out of critical parts such as fasteners, brackets, and pole hardware, is ideal.
Thermal Zinc Diffusion (TZD) is being proven worldwide to have ideal properties to protect critical components due to the nature of the dry baking process reducing hydrogen rather than inducing it.
TZD is also suitable for use with high tensile steel grades, with hydrogen embrittlement concerns removed. Steel grades at tensile strengths greater than 800 MPa are typically at risk of hydrogen embrittlement.
TZD does not employ acid pickling, but typically utilises shot blasting for surface preparation, permitted by the greater diffusion time and increased development of the TZD gamma layer. The layers of TZD are typically harder than that of the parent material typically exceeding 35 Rockwell C (ASTM A1059/A) resulting in excellent wear resistance properties.
Higher-tensile products such as critical fasteners can also have TZD protection, while the thread will have no galling issues, with the even coating consistency enabling torque and tension performance to be more accurately achieved.
ArmorGalv in Thornton, New South Wales, is Australia’s only plant providing TZD, and has recently expanded to a larger facility adding new equipment to cope with the growing demands of a new forward-thinking Australian industry; demanding non-toxic environmentally friendly solutions.
ArmorGalv is also launching ArmorThread to support industry with high-tensile corrosion protection without hydrogen embrittlement.
This sponsored editorial is brought to you by ArmorGalv. For more information, call 02 4028 6760, email sales@armorgalv.com.au, or visit: www.armorgalv.com.au.
