Choosing the Proper Glycol
- An inhibited propylene glycol such as “DowFrost” is best.
- DowFrost contains special corrosion inhibitors for low system maintenance and better heat transfer compared to other glycols.
- It also has a longer fluid life, up to 20 years in some cases.
- Use of Uninhibited Glycol
- Even through uninhibited glycols do lower the freeze point, they are often more corrosive than water.
- The corrosion rate of ethylene glycol on iron, for example, is more than 2.5 times faster than plain water. On steel, it is 4.5 times faster.
- Automotive Based Antifreeze
- Automotive based antifreeze Should never be used!
- Automotive antifreeze contains silicate based inhibitors, which are compatible with automotive components.
- In an industrial application, the silicates will coat the heat transfer surfaces and reduce the cooling efficiency of the system.
- Silicates can also significantly reduce the life of pump seals.
- Sources of Inhibited Propylene Glycol
- For a complete literature package, material, safety data sheets and purchasing information, contact the following: Dow Chemical 1-800-447-4369 (Canada 1-800-363-6250) Dowfrost inhibited propylene glycol.
- A refractometer should be used on a regular basis to determine the mixture strength according to freeze point.
Misco Products Model #7084VP
- The coolant freeze point is indicated on the line between the dark and light areas on the scale. In this example, the freeze point is about -5°F to -6°F.
- The freeze point temperature should be 25°F below the lowest required setpoint (see chart).
- Water evaporates from the mixture, and if you continue to add a premixed solution, eventually you will have too much glycol.
- It is necessary to add water or glycol to maintain proper freeze point temperature.
- The refractometer pictured is accurate and easy to use for maintaining and checking for proper glycol levels.
Freeze Points for Water/Propylene Glycol Solutions
Percentage of Glycol*
Percentage of Water
Note: Glycol freeze point must be 25°F below lowest setpoint.