Prometheus21
Mechanical
- Apr 22, 2023
- 104
Hello everyone,
I'm unsure of whether to post this under chemical, corrosion or metallurgy, so my apologies beforehand if this question is outside the scope of this forum.
Back in the 60's my company had a special degreasing/surface treatment process designed for their manufacturing purposes. Parts made of brass (CW614N), SS (316L), Copper and Monel 400 can all be dipped in these baths for degreasing and surface treatment (316L would just be degreased as no other chemical reaction happens during this process).
After an initial pre-cleaning using a strong alkaline solution followed by a rinse in water the product is dipped in a solution combined of 62% nitric acid, non iodized salt and some small amounts of carbon black. This is followed up by some other chemical baths (piranha solution with red spirit) + sulfuric acid with an added corrosion inhibitor).
My question is this: what is the purpose of using the non iodized salt and the carbon black in combination with nitric acid? I have seen many other manufacturing plants using it as well, but are unable to answer this question. It seems to be something people have been doing for decades, but the knowledge as to why has been lost. "But hey it works, so don't change it."
Thank you for any input you may have.
I'm unsure of whether to post this under chemical, corrosion or metallurgy, so my apologies beforehand if this question is outside the scope of this forum.
Back in the 60's my company had a special degreasing/surface treatment process designed for their manufacturing purposes. Parts made of brass (CW614N), SS (316L), Copper and Monel 400 can all be dipped in these baths for degreasing and surface treatment (316L would just be degreased as no other chemical reaction happens during this process).
After an initial pre-cleaning using a strong alkaline solution followed by a rinse in water the product is dipped in a solution combined of 62% nitric acid, non iodized salt and some small amounts of carbon black. This is followed up by some other chemical baths (piranha solution with red spirit) + sulfuric acid with an added corrosion inhibitor).
My question is this: what is the purpose of using the non iodized salt and the carbon black in combination with nitric acid? I have seen many other manufacturing plants using it as well, but are unable to answer this question. It seems to be something people have been doing for decades, but the knowledge as to why has been lost. "But hey it works, so don't change it."
Thank you for any input you may have.
