Engine coolants corrosion inhibition

Dissolved solid and gaseous impurities can also affect the pH of the system and this may often lead to decreased inhibitor efficiency. In industrial plant, cooling waters can take up SOj, HjS or ammonia and pH control of inhibited waters will be necessary. The leakage of exhaust gases into engine coolants is an example in which corrosion can occur despite the presence of inhibitors. 

There has been much activity in this field of corrosion inhibition in recent years which appears to have been prompted by health and safety requirements. As with engine coolants, the use of nitrites, particularly where amines may also be present, needs to be considered carefully. Nitrites have been widely used in cutting, grinding, penetrating, drawing and hydraulic oils. Suggested replacements for nitrites and/or amines make use, inter alia, of various borate compounds, e.g. monoalkanolamide borates. Molybdates have also been proposed in conjunction with other inhibitors, e.g. carbox-ylates, phosphates, etc . Water-based metalworking fluids usually contain other additives in addition to corrosion inhibitors, e.g. for hard-water stability, anti-foam, bactericidal proderties and so on. Thus, claims are made for oil-in-water emulsions with bactericidal and anti-corrosion properties. 

Testing corrosion inhibiting, engine coolant concentrate ( antifreeze )... 

Chem. Analysis Sodium benzoate (90-92%), sodium nitrite (8-10%) Uses Corrosion inhibitor for antifreeze, closed cycle heating and cooling systems, domestic and industrial heating systems, summer coolants for internal combustion engines, hydraulic systems, emulsion paints, textile emulsions and adhesives corrosion-inhibiting impregnant for wrapping papers... 

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