Chloride Residue Removal And Testing

Chloride Residue Removal And Testing

Dip Brazing occurs in a liquid salt bath at a temperature of approximately 1100 degrees F. Brazing salt turns liquidus as it is heated and turns solidus as it cools. The resulting cooled salt can lead to entrapment and contamination that can result in part deterioration if the salt is not removed.

Brazing specs call for chloride residue removal to less than 5 PPM (parts per million) of residue. Most exterior salt is commonly removed by immersion of the brazed assembly in agitated hot water and proper rinsing. We assist this process by utilizing chemicals that help release the salt from the aluminum surfaces, ultrasonic cleaning tanks that ultrasonically clean the assemblies and filtering our tanks to remove the salt that has been removed from the assemblies. The inclusion of ultrasonic cleaning in our process allows us to remove salt from fin stock, blind holes and threaded inserts.

We test for chloride residue removal by using two methods of inspection. The most commonly used method in the industry is the use of a silver nitrate compound. By using silver nitrate with a proper sample of rinse water from the brazed assembly and inspecting the sample for water clarity, it can be determined that the part is free of salt contamination. Although the resulting sample can determine that there is little residue, it does not quantify the exact PPM of residue present.

A more accurate result can de achieved by using a properly calibrated water purity meter. We also test for chloride residue by using a calibrated Myron L water purity meter and probe that has been calibrated for chloride content. This results in more accurate inspection results and allows us to accurately state that our assemblies meet the requirements of our customers and the brazing specifications.