TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - The brazed aluminum surface comprises residual flux agent. The residual flux agent comprises halogen atoms, alkaline earth metal halogen compound, or alkaline metal halogen compound. The halogen atoms are fluorine atoms. The residual flux agent preferably comprises a mixture of potassium aluminum hexafluoride, potassium aluminum heptafluoride, or potassium aluminum tetrafluoride.    TECHNOLOGY FOCUS - MECHANICAL ENGINEERING - Preferred Components: The system includes an ion exchange resin in contact with the coolant, heat exchanger configured to transfer heat between the two cooling subsystems. The cooling system can also comprise two first cooling subsystems, and two coolants. The cooling system component(s) comprises a brazed metal surface. The second coolant does not contact the first cooling subsystem. The second coolant does not contact a brazed. The second cooling subsystem is configured to cool a fuel cell.    TECHNOLOGY FOCUS - METALLURGY - Preferred Components: The brazed aluminum surface comprises residual flux agent. The corrosion inhibitor is a copper alloy corrosion inhibitor. The copper alloy corrosion inhibitor is an azole compound. The corrosion inhibitor is an aluminum-ferrous metal corrosion inhibitor. The aluminum-ferrous metal corrosion inhibitor is a silicate, a carboxylate, a phosphate, a borate, a molybdate, a nitrate, a nitrite, an alkali metal, an alkaline earth metal, ammonium, and/or an amine salt.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The alcohol is methanol; ethanol; propanol; butanol; furfurol; furfuryl alcohol; tetrahydrofurfuryl alcohol; ethoxylated furfuryl alcohol; ethylene glycol; diethylene glycol; triethylene glycol; 1,2,-propylene glycol; 1,3,-propylene glycol; dipropylene glycol; butylene glycols; glycerol; glycerol-1,2-dimethyl ether; glycerol-1,3 dimethyl ether; mono ethylether of glycerol; sorbitol; 1,2,6-hexanetriol; trimethylpropane; and/or alkoxy alkanols.    TECHNOLOGY FOCUS - POLYMERS - Preferred Components: The poly carboxylic acid functional compound comprises acid functional corrosion inhibiting component (10-100 wt. %), corrosion inhibitor (0.1-4%). The coolant comprises acid functional corrosion inhibiting component (1-10, preferably 2-4 wt. %). The corrosion inhibiting coolant includes additive(s), alcohol(s), corrosion inhibitor different from polycarboxylic acid functional corrosion inhibiting component. The additive is colorants, dispersants, antiscalants, wetting agents, biocides, pH adjusting agent, and/or buffering agents. The polycarboxylic acid functional compound comprises a tall oil fatty acid derived from a cyclohexenoic acid containing compound. The cyclohexenoic containing compound comprises a maleated tall oil fatty acid, a maleated tall oil fatty acid salt, a reaction product derived from a maleated tall oil fatty acid, a reaction product derived from a maleated tall oil fatty acid salt, a reaction product derived from a ethylene glycol ester, a reaction product derived from a ethylene glycol ester salt, or a maleated tall oil. The polycarboxylic acid functional compound comprises a maleinized unsaturated fatty acid, acrylate copolymer, a styrene copolymer, or a polymerizable acid graft polymer. Preferred Definitions:    R1 = a group of structure (CH)x-(COO)-((CH2)y-O)z-H;    R2 = COOH or anhydride group with R3;    R3 = H, COOH or anhydride group with R2;    R4 = 1-10C alkyl group;    x, z = 0-5; and    y = 1-5.    EXAMPLE - A coolant composition containing monocarboxylate acid based coolant (25%), tail oil fatty acid derived compounds (0.1-0.3 wt. %), and chloride ions (100 parts per million) was prepared and tested for its corrosion protection ability. The result showed that the coolant containing organic acids, low silicate hybrid and high silicate based corrosion inhibitor formulation can provide excellent corrosion protection for aluminum alloys in vehicle operation conditions, and provides improvement in corrosion protection of brazed aluminum with fluoride based flux residual.