Nitrate salts are generally very easy to handle with an approximate working temperature range from 350-1000°F.
It should be noted that if the salt splashes (for whatever reason) onto the skin and safety clothing is not worn, the salt will keep on burning into the skin until the salt cools down to a solid. This can create very nasty burns that will take a long time to heal. When loading the work into the salt bath, safety clothing should be worn.
Careful preheating of the workpiece and work basket is important to remove any residual moisture that might be present on the basket or component. Care must also be taken with any residual surface salt that might be adhering to the workpiece. Most of the heat-treatment salts are considered poisonous, so a very thorough washing procedure must be used to remove any traces of residual-salt adherence.
I do not know the circumstances that caused one recent accident, and I do not intend to speculate on what really did happen. However, having been a heat treater on the shop floor with heat-treatment salts and selling heat-treatment salts, I know that care must be taken with the handling and use of both slats and the process furnace.
This is why The Metal Treating Institute (MTI) is so big on training. MTI suggests training for
- Confined-space entry
- Safe handling and usage of heat-treatment salts
- Safety in heat treatment
- Equipment maintenance
- Secure storage of heat-treatment salts
Handled correctly and in a very responsible manner, heat-treatment salts are an inexpensive method of heat treating both steel and aluminum. They are also safe to handle, provided that one fully understands the nature of the salts and what they have the potential to accomplish. Train your operations people, train your management, train maintenance, train your safety teams and train your accident teams in the use of salt baths. In particular, get the best understanding possible of both salts and confined-space entry.
Remember that things are hot and can burn you in a heat-treatment shot. On top of that, accidents can and will happen.