Why I Now Check Coolant pH Level Every Week
A batch of hydraulic cylinders came out with a strange discoloration on the bore surface. The dimensions were fine. The surface finish was fine. But the parts looked wrong. The customer rejected the whole batch. I checked the coolant and found the pH had dropped to 7.5. The coolant had gone acidic, which caused it to etch the steel surface. The discoloration was light surface corrosion. The fix was simple. I changed the coolant and added biocide to prevent bacterial growth. The pH returned to 9.5 and the next batch was fine. But the rejected batch was a total loss. The cost of those cylinders was several thousand dollars. ...