Salt bath curing

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Salt bath curing:

In salt bath method, the product goes directly into a short conveyor belt down into a tank filled with a melt of liquid tanks. The width and depth of the tank varies depending on the size of the product to be manufactured.



  • The most common salt mixture used is a blend of sodium nitrite and potassium nitrate with the addition of a certain amount of sodium nitrite which is heated to a temp between 180°to 240° Celsius.
  • During the conveyance through the salt bath, the product must be pressed down underneath the surface with the aid of conveyor belts or rollers.
  • In the manufacturing of complicated products such as certain rubber profiles, spray nozzles are used to shower the salt mixture over the profiles . In this way the deformation forces from conveyor belts and rollers are avoided. Using high temp the process can be carried out at high speed.
  • After the curing by the salt bath method, the salt must be washed off and the products must be cooled. 
  • Finally the finished product is made available greatest advantage of this method is that the salt provides very fast heat transmission to the products which are to be manufactured. The disadvantages are the negative environmental aspects of the process.
  • The salts which are used are classified as toxic substances due to the sodium nitrite content and can, in the event of a fire act as a fuel for combustible materials.
  • There are stringent requirements on cleaning the rinsing water, which contains a lot of dissolved salt. 
  • A common method of purification is to boil off the water and recycle the residual salt.
  • A method that is somewhat gentler to the environment is using a salt where the sodium nitrite is replaced by lithium nitrate.
  • The disadvantage of the  salt bath is that it has been associated with the formation of nitrosamines which are suspected human carcinogens. These chemicals are formed when a notrogen and an Oxygen from a Nitrosating compound bind to the amino group Nitrogen of the amine compound.

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