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Monitor SCA, Inhibitor Levels for Metal Protection, Fluid Stabilization

Supplemental Coolant Additives (SCA) and inhibitor formulations protect cooling system components, minimize the chemical reactions that occur due to heat, control scale formation, prevent foaming and maintain pH. SCA and inhibitors are very concentrated packages that not only contain many of the same inhibitors found in antifreeze but also some that are much more sophisticated, such as:

  • pH Buffers

  • Dispersing Agents

    • water only coolant at 180°F can hold up to 15 ppm calcium hardness in a dissolved state

    • Water and 50% antifreeze can hold up to about 70 ppm total hardness in a dissolved state

    • Water, 50% antifreeze and proper levels of supplemental coolant inhibitors can hold up to about 200 ppm total hardness in a dissolved state

  • Dissolved Gas Scavengers and Neutralizers

  • Filming Agents

    • Prime Protection for Metal Pitting or Deposit

Ideally, nitrite-based formulas should contain between 1000 and 3200 ppm nitrite for adequate metal protection. Nitrite levels above 3400 ppm can cause precipitation that can plug the system.

A nitrite/molybdate formula should contain a combination of the two equal to no less than 780 ppm with nitrite at no lower that 300 ppm. This includes Extended Life formulations as well. Nitrite/molybdate combinations exceeding 3400 ppm can cause precipitation that can plug the system.

Always check your engine manufacturer's specifications before using any coolant formulation. Never use a water only coolant or a water and glycol only coolant as neither has the additives necessary for adequate engine metal protection.

SCA Functions & Limitations
Additive Function Limitations
Phosphate Iron protection; pH control Relatively rapid depletion rate; Poor stability at high temperatures
Borates Iron protection; pH control Corrosive to aluminum at high temperatures
Molybdate Iron protection  
Dicarboxylate Iron & aluminum protection  
Carboxylate Iron & aluminum protection  
Mercaptobenzothiozole (MBT) Copper & brass protection Formulation of insoluble calcium salts
Tolytriazole (TT) Copper & brass protection  
Nitrate Aluminum & solder protection  
Silicate Aluminum protection Creates precipitates if pH drops or hard water enters system; can form hard, insulating scale
Nitrite Cast iron, steel and liner cavitation protection Rapid depletion rate; Nitrosamine formation when amines present
Silicones Defoamant  
Block Polymers Defoamant; Scale & deposit control  
Dispersants Scale & deposit control  
Sufactants Scale & deposit control  
Sebacates   Expensive; Poor aluminum protection

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