The choice of materials is an important factor in reducing risk, ensuring the long-term safety and performance of pipes and components.
Low carbon alloys should be considered when looking for stainless steels with excellent resistance to intergranular corrosion.
When selecting a low carbon alloy, a selection with a carbon content less than 0.03% will ensure that carbides form an insufficient amount of carbon.
If a low-carbon alloy is not suitable for your intended use, alloys with titanium or niobium additions can also provide excellent intergranular corrosion resistance.
However, alloys with titanium or niobium added are susceptible to a particular form of intergranular corrosion called knife-line attack.
This happens when carbon interacts with titanium or niobium instead of chromium. Fortunately, heat treatment usually solves this problem and restores the metal structure to a near original state.
In some cases, solution-annealing (also known as quench-annealing or solution-quenching) is an effective means of reversing intergranular corrosion damage in austenitic stainless steels.
Once heated, the metal is water quenched, rapidly cooling it and solidifying the grain and structure.
Unfortunately, the method is less than ideal for treating large assemblies. Also, it does nothing to protect pipes or other components from damage later should welding or repairs occur.