Summary for caustic soda etch tank Discussion
Caustic soda etch tank issues are raised by Douglas Marden, who reports that an Oakite 160 (NaOH) aluminum etch tank had run for eight years without any intergranular attack on quarterly 2024 bare aluminum test panels, but suddenly failed two separate lots. He notes the tank is routinely dumped at 49% and that the test specimens come from the inspection company, so he doubts the material is the cause. The excerpt provided contains only the question and no posted replies, so there is no named answerer or confirmed root cause in the source. The practical takeaway from the thread as shown is simply that a new process or bath condition change should be investigated rather than assuming the test material is at fault.
Q. We have a chemical etch tank that is made up with Oakite 160 (NaOH) and used exclusively for etching aluminum. The tank’s maintenance includes routine 49% dumps. Every three months, we process test panels that are made up from 2024 bare aluminum and have them inspected for intergranular attack and end grain pitting. After 8 years of maintaining this chemical processing line, we have never had any intergranular attack detected until now. The test specimens we processed in the tank are provided to us by the company that performs the intergranular attack and end grain pitting inspection and tests were conducted with material from to separate lots, so we don’t believe the reason for the failure is due to the material. Any suggestions as to a possible reason for the sudden intergranular attack would be appreciated.
Douglas Marden
– Sandpoint Idaho
June 6, 2021