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What is Hydrogen Embrittlement, and why thermo-diffusion zinc coating is the best way to avoid it?

What is hydrogen embrittlement?

Hydrogen embrittlement is a phenomenon that can significantly compromise the mechanical properties of metals, particularly high-strength steel. It occurs when hydrogen atoms are introduced into the metal, usually through corrosion reactions, plating processes, welding, or cathodic protection. When the metal is subjected to stress, the hydrogen atoms can migrate to areas of high-stress concentration and cause premature failure.

Although HE can cause various types of damage, cracking is the most common. Different types of cracking are caused by different impacts on ductility, different environments, and different stresses.

Generally, hydrogen penetration into metals occurs as a result of metals reacting with acids or electrolytes. The most common type of cracking is Stress Corrosion Cracking (SCC). It is caused by the combined action of tensile stress and a corrosive environment. SCC can cause irreversible damage to metal components, leading to costly repairs and downtime.

A damaged steel structure would need to be replaced or repaired relatively quickly, and it may collapse over time. Second, the oil and gas industry faces a second risk from leaks, fires, and explosions caused by large quantities of hydrogen leaving infrastructure.

Though it can take years for hydrogen embrittlement to cause an infrastructure to collapse, when the time comes, the consequences are often severe. The relatively slow process does not imply that proper safety measures to prevent hydrogen embrittlement are not essential.

In this video, you can see a tangible example of the dangers associated with hydrogen embrittlement, when in 2014, large and heavy bolts from the support structure of London’s Leadenhall building, known as “The Cheese Grater,” began falling to the street below, posing a risk to pedestrians.

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How to avoid hydrogen embrittlement?

Some anti-corrosion coating methods, even very common ones such as Hot-Dip Galvanizing and Electroplating, are subject to Hydrogen Embrittlement due to the involvement of acids or electrolytes during the process.

There are different methods to prevent hydrogen embrittlement. The main solution is heat treatment, during which the parts are heated at a relatively high temperature over time to drive out diffused hydrogen.

However, this “baking” method to mitigate hydrogen embrittlement (used mainly post-electroplating) presents several challenges. While it can effectively release diffused hydrogen, it introduces added costs due to energy consumption and equipment investment. The process can be time-consuming, potentially slowing production.

How does Distek’s thermo-diffusion zinc coating process solve it?

The Distek (Armorgalv®) process is a 21st-century form of the well-established, 115-year-old zinc thermal diffusion process (TDG).

TDG technology, developed by Distek (Armorgalv®), involves mixing steel products with Distek’s patented dry zinc powder and slowly heating them at 320-470°C in a rotating, sealed container inside an oven. The process is also eco-friendly and does not involve acids or hazardous materials.

The fact that Distek’s thermo-diffusion zinc coating process includes no acids and the products are also slowly heated as an inherent part of the process makes it an ideal way to avoid hydrogen embrittlement damages and costs.

Here are the test results made by Spencer Industries of heat-treated grade 8 bolts coated by Distek’s thermo diffusion zinc method. The results of this inspection showed that there were no cracks, linear indications, and/or evidence of hydrogen embrittlement.

 

Distek’s coating method has also been proven to provide better-quality protection through stronger corrosion resistance. Testing has shown the coating stands up to the most extreme conditions, including 3,000 hours of salt spray testing. It is 5–10 times better than hot-dip galvanizing (HDG). 

Distek works closely with customers to plan and install its anti-corrosion coating lines, as well as provide technical support. After discussing your company’s specific needs, our experts will plan, design, and produce the most suitable coating line for your business. 

Providing an attractive cost-benefit ratio and a superior anti-corrosion solution, it’s easy to see why Distek has been chosen by dozens of clients around the world.

 

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