Degreasing bath control parameters
|Bath concentration for immersion||5%|
|Bath temperature||30 deg. C min. 60 deg. C max.|
|Immersion time||5 minutes to 10 minutes|
|Free alkali, points||20 to 35|
|Total alkali / Free alkali ratio||< 3.0|
Testing and Control:
Warning: Do not pippette by mouth, use a pro-pipette.
Pipet a 10 ml degreasing bath sample solution into a 150-ml beaker. Add 5 drops of phenolphthalein indicator. Titrate with Standard Acid Titrating Solution (0.1 N H2SO4) to the end point. Disappearance of pink colour is the end point. The volume of the titrating solution is the free alkali value in points.
Disappearance of pink colour – End point
Pipet a 10 ml of degreasing bath solution sample into a 150-ml beaker. Add 5 drops of bromocresol indicator solution. Titrate against with the Standard Acid Titrating Solution (0.1 N H2SO4) to the end point. Appearance of pale green from blue colour is the end point. The volume of Titrating Solution is the total alkali value in the alkali bath.
End point: Blue to green
Total Alkali/Free Alkali Ratio:
As the degreasing bath is used regularly and frequently, it becomes contaminated, and the total alkali value will rise. Thus, the ratio of the total alkali value to the free alkali value will also rise and this becomes a useful measure of the degree of contamination of the cleaner solution. The solution is periodically dumped or continuously overflowed to keep the total alkali to free alkali ratio from exceeding the maximum value determined for the system. Total Alkali/Free Alkali Ratio should be regularly monitored. The value under typical cleaning conditions should not be allowed to exceed 3.0.