Summary for sulfuric acid conductivity Discussion
sulfuric acid conductivity in anodising cannot be judged reliably by color or specific gravity, according to James Watts. In response to S Tambe’s question about a home anodising bath that seems to lose throwing power after 2 to 6 months, Watts says the solution will not perform as well as a relatively fresh bath. He recommends a simple chemistry titration to determine whether more acid should be added, and notes that a more involved titration can show when the bath should be discarded because of excessive aluminum buildup. He also warns that testing for copper and other alloy contaminants is much more complicated. Specific gravity is not a dependable check because dissolved metals distort the reading. Watts adds that bath life can be extended by routine titration, and that in some cases it may be economical to keep using the bath until product quality drops, then dump most of the tank.
Q. Dear sir,
I am a home type anodiser doing small scale sulfuric anodising process for labels.
After some time, say 2 to 6 months, it seems that throwing power of solution is reduced considerably. Is there any technique by which we can confidently say that yes solution has become weak and needs to be replaced. Or, to say it another way, any thumbrule by which we can judge that solution is to be discarded say by observing its colour, or specific gravity etc. Or is it possible that we add fresh acid in the above solution and it will be useful and will give results same as fresh solution.
Thanks
S Tambe
– Raipur, Chhattisgarh, India
December 21, 2011
December 21, 2011
No, it will not be as good as a relatively fresh solution.
Simple chemistry titration will tell you if you need to add acid. A less simple titration will tell you if you need to trash the solution because of excessive aluminum in it. Testing for copper and other alloy components is far more complicated.
You can extend the life of your solution by doing a simple acid titration mentioned above. Do not use specific gravity because it also includes dissolved metals giving you a false reading.
Depending on the haz waste treatments required in your country, it may be cost effective to use it as long as the product is OK and then dump 95% of the tank.
James Watts
– Navarre, Florida