Cooling water treatment is carried out to prevent corrosion. This is because distilled water has the tendency to absorb CO2, O2. CO2 FORMS CARBONIC ACID. It leads to rust in presence of O2.
Type of cooling water inhibitors :-
1. Nitrite / Borate :- Borate adjust cooling water pH to give slight alkalinity.
ADVANTAGES:-
1. It is an O2 scavenger.
2. Compatible with anti freeze
3. Disposal of cooling water does not causes any environmental hazards.
4. Can be used for JCW fresh water generator.
DISADVANTAGES:-
1. Does not passivate against zinc anode.
2. Attack soft solder.
2. Chromate:-
ADVANTAGES:-
1. Very effective corrosion inhibitor.
2. Can be used in presence of zinc anode.
DISADVANTAGES:-
1. Must be handled carefully to avoid skin or eyes contact.
2. Cannot be used in JCW in fresh water generator.
3. Hazard to environment.
4. Incompatible with anti freeze.
5. Does not act as pH buffer.
3. Soluble Oil :-
ADVNTAGES:-
1. Safe to handle.
2. Can be used for fresh water generation.
3. Reduce cavitation damages.
4. Good protection on clear metal surface.
DISADVANTAGES:-
1. If water is not sufficient then oil separated.
2. Disposal is a problem.
3. Tendency to foam which can interrupt flow rate.
4. Form heat insulating layer.
5. High concentration can lead to overheating.
4. Elysator:-
It is a non chemical water treatment of any enclosed fresh water system to prevent all kind of corrosion. Here a magnesium sacrifised instead of the system. During the process the O2 in water will be consumed creating H2O and Mg(OH)2.