Methods and compositions for passivating heat exchanger systems

Abstract

A method for treating parts in a heat exchanger system is provided. In the method, heat exchanger parts with metal surfaces which chemically and detrimentally interact with additives in coolant fluids in the heat exchanger system are treated by contacting the metal surfaces with a phosphate-containing solution for the phosphate-containing solution to passivate the metal surface for subsequent contact with the coolant fluids.

Description

[0001]This application claims the benefit of U.S. Provisional Application No. 60 / 953,626, filed Aug. 2, 2007.FIELD OF THE INVENTION[0002]The invention relates generally to compositions and methods for passivating surfaces of components and parts in heat exchanger systems that employ coolants for heat transfer.BACKGROUND[0003]Methods for producing heat exchange systems have changed over the years with increased used for lighter materials such as aluminium and alloys thereof. Construction methods have also changed with the use of brazing, e.g., controlled atmosphere brazing or CAB with the brazing in a controlled N2 gas environment using a potassium fluoroaluminate flux. Flux is applied to the surfaces of the heat exchange parts to be joined, the assembled unit is heated in a N2 environment, and joining occurs.[0004]Coolants (heat transfer fluids) are used to take away heat from heat exchange systems such as engines. It is known to add corrosion inhibitors to coolants to reduce corros...

AI Technical Summary

Benefits of technology

[0009]In another aspect, the invention relates to the use of a phosphate-containing solution having a pH of 4.0-12.0 and containing 0.005 to 30 g / l of phosphate ions to treat parts in a heat exchanger system, which parts have metal surface that chemically and detrimentally interact with additives in coolant fluids in the heat exchanger system. In the treatment process, the phosphate ions in the phosphate-containing solution reduce the chemical activity of the metal surface for subsequent contact with the coolant fluid.

Problems solved by technology

Recent investigations show that the presence of flux in heat exchanger systems such as radiators generally leads to an increase in the corrosion rate of coolant fluids used in the systems.

Other tests have shown a fast depletion of some coolant inhibitors in heat exchangers, specifically nitrogen and silicate-based inhibitors, along with an increase in the pH of the coolant fluids used in the systems which severely impact the performance of the coolant.

However, phosphate salts although known to inhibit aluminum corrosion, are unacceptable to a number of original equipment manufactures.