Abstract
Tests are described covering two winter seasons of automobile and truck operation with methanol anti-freeze containing chromate, with and without supplementary additions of borax, tetrasodium pyrophosphate or sodium metasilicate. From 2 to 6 coolant inspections were made in the 17 vehicles tested over operating periods ranging from 1.6 to 5.8 months. Results demonstrated the chemical stability of chromate in this use. Laboratory observations indicated that compatibility depends on shielding from light. Engine disassembly and examination confirmed that cooling systems in which chromate was used not only were protected from corrosion, but remained cleaner in regard to surface deposits than uninhibited systems.
Because chromate tends to loosen rust and deposits, pre-cleaning before charging old systems with chromated methanol antifreeze is recommended. The advantage of using chromate in cooling water to prevent corrosion and deposit formation during the summer is underlined.
For packaged antifreeze the low solubility of sodium chromate in methanol was found to necessitate adding some water in order to obtain an adequate inhibitor concentration. An alternative is to use lithium chromate which is amply soluble in methanol.
