Work Item
ASTM WK83357

Revision of D1121-11(2020) Standard Test Method for Reserve Alkalinity of Engine Coolants and Antirusts


It seems to me that D1121 is written with a classic buret-titration in mind, for example it requires the drop wise titration rate.
It would be better define the rate in mL/min, because today the most labs are using an automatic titrator.
Labs measure the Initial pH and then titrate very slowly with an automatic titrator to a pH 5.5.
We also titrate for a lot of samples to an inflection point, on the titration curve we can always determine the RA at 5.5.

There have been some troubles with the electrode for Reserve Alkalinity. A classic pH electrode wasn’t good enough for some coolants. The problem was that after titration the electrode couldn’t be used anymore. Every result after the titration of that product becomes lower and lower. Even after cleaning and stabilizing the electrode the results stay too low.
Now we use an electrode with combined pH electrode with double-junction.

About automatization.
In D1121 you need to clean and dry the electrode with a dry cloth or tissue to remove excess water. Because of this sentence, its seems that you can’t automate the test, but there are companies that sell automatic devices for this test.
It is outdated to have a titration norm that doesn’t accommodate automatization. It is proposed that an alternative, autmatic titrator method be included in D1121.


Developed by Subcommittee: D15.04

Committee: D15

Staff Manager: Ashley Wiand

Work Item Status

Date Initiated: 09-05-2022

Technical Contact: Edward Eaton

Item: 000