Sodium Hydroxide is a highly corrosive salt. How to safeguard the neighbor materials associated with it from its corrosive action?
Changing the material of tubes should be better.
NICKEL ALLOYS is a good opition. Generally speaking, nickel alloys are more expensive than stainless steels.
You can choose the alloy according to the temperature and concentration in the tube.
A link for ref:
https://e-reports-ext.llnl.gov/pdf/326030.pdf
Changing the material of tubes should be better.
NICKEL ALLOYS is a good opition. Generally speaking, nickel alloys are more expensive than stainless steels.
You can choose the alloy according to the temperature and concentration in the tube.
A link for ref:
https://e-reports-ext.llnl.gov/pdf/326030.pdf
If you are stuck using 316SS and cannot keep the NaOH away, you probably will end up using a two part epoxy. However, you should check with the manufacturer of any potential epoxy to confirm that it is reasonably resistant to issues where the caustic would result in disbonding of the paint from the metal. You should also ask them about the recommended surface preparation for the 316 since getting an acceptable level paint adherence to a smooth stainless surface is not a simple matter.
If it is possible to heat the painted surface to 250 to 300 degrees F to promote a cure, then use of an epoxy phenolic coating would provide better service than other epoxies that are applied at ambient temperature.
Use can also try exploring the thermal spray coatings. They are highly industrialized and mostly recommended for protection against corrosion/Wear.
The corrosion resistances of 316SS and 316L are essentially the same and these days most 316SS that is purchased is also dual certified as 316L. When higher strength levels are required for this class of material, the non-L grade selection is usually 304 rather than the non-L grade of 316SS.
Both 316 and 316L have good resistance to pure NaOH. The corrosion problem between 316 (or 316L) and NaOH is that there is usually some degree of contamination of the NaOH with NaCl. It only takes a few hundreds of ppm of chloride to cause pitting corrosion at lower temperatures and cracking issues above about 50C (depending upon the strength of the material). Coating with an organic paint will help extend the life of existing equipment when the issue is pitting corrosion but will not address cracking. Thermal sprays with more corrosion resistant Ni or Cr based materials (and definitely not aluminum or aluminum zinc) will only work if thermal spray coating that is applied has very low porosity (which is not always a foregone conclusion).
Using High velocity oxy-fuel (HVOF) and Detonation gun (DS) thermal spraying systems, coatings with even < 1% porosity can be obtained. Cold spraying could also be useful in developing low porosity content coatings.
Thanks a lot for all for the inputs - Can anybody provide some manufacturer details who deals with nickel alloyed paints.
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