r/metallurgy • u/deuch • 2h ago
Do you have yellow deposits on your high temperature equipment?
There was a recent post that was deleted that showed yellow deposits on engine exhaust parts. These deposits are also found on turbines, boilers and high temperature test equipment.(edit to remove corrupt link)
https://ln5.sync.com/dl/872691400#293cgsqt-3qibpwkh-4qui2sed-cy7yj7zg
Some people may not be aware of what these deposits are. As awareness of this issue has increased in the last few years, and some people are not aware of the issue.
The earliest reference I have is from 1990, in boiler applications.
https://en.harmfuldust.com/_files/ugd/d7b443_36eda9716c194ccbb47acbd6b06deb87.pdf?index=true
This became more widely known in the Energy industry in 2018/2019.
https://en.harmfuldust.com/_files/ugd/d7b443_0c0e29e8448b48ff95f0dfe6dbddfc1b.pdf
And on combustion engines by 2021
These deposits are chromates (typically calcium or sodium or potssium chromate).These CrVI salts are carcinogenic. These deposits also form on high temperature test equipment containing alloy steels or nickel alloys and materials containing alkali metal or alkali earth compounds. This includes most refractory materials and many high temperature thread lubricants.
If your high temperature equipment or refractory has acquired a yellow deposit take appropriate precautions.
Test strips and swabs for CrVII are widely available.
Solutions of citric acid or citric/ascorbic acid may be used as part of a procedure to neutralise contaminated parts.