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A multi-metal corrosion inhibitor was tested in potassium formate (HCOOK) solutions. The results showed that the inhibitor could provide full protection on mild steel, aluminum, copper, and brass, and good protection on soft solder. For cast iron, a secondary inhibitor would be needed to provide protection against pitting and crevice corrosion.
Potassium formate (HCOOK) aquesolutions (or brines) have been used as heat transfer fluids or antifreezes for process cooling, deicing, and other applications. ut The brines have excellent thermophysical properties such as high thermal conductivity, high specific heat capacity, and low freezing point; are nonflammable and environmentally friendly; and also offer several advantages over some traditional heat transfer fluids and brines. They are thermally more stable than glycols, nontoxic compared to ethylene glycol, less viscous than propylene glycol, and less corrosive than calcium chloride (CaCl^sub 2^) brines.
Process cooling systems often consist of multiple metals and materials exposed to heat transfer fluids. Compatibility in terms of corrosion performance of the metals and materials in the heat transfer fluid is one important consideration in process design and materials selection. Considering that HCOOK solutions are brines in nature, corrosion properties of the solutions are of concern. An uninhibited fluid or coolant can be very corrosive (to some materials), which is also true for non-brine fluids such as glycols.4 Corrosion inhibitor additives are thus needed for proper operation.
In this study, a commercially available corrosion inhibitor, Dynalene V1[dagger] composed of proprietary carboxylic acid amine, is added to inhibit corrosion of ferrous and non-ferrous metals in 42% HCOOK aqueous solutions, and tested at different temperatures by electrochemical and immersion testing methods.
Experimental Procedure
Electrochemical Testing
The materials for testing were aluminum (UNS A93003), carbon steel (CS) (JJNS G W 180), gray cast iron (UNS F10007), copper (UNS C10100), brass (UNS C23000), and Sn96Ag4 solder. The tin-silver solder specimens were cut from a spool of commercially available wire (3.2 mm in diameter) and straightened. The cast iron specimens were flat and rectangular in shape. All other metal specimens were machined rods, 1 2.7 mm in length and 9.5 mm in diameter per ASTM Go.'1 The exposed area of the specimens was polished with 600 and 1,200 grit silicon carbide (SiC) papers, cleaned with Kimwipes* in tap water, rinsed with...