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Problematic Rinsing of Etching Solution from Aluminum Extrusion

I am having problems rinsing this piece after caustic etch. Sketch is attached.
The part is a 20 ft extrusion of 6063 AL. I can rinse this part a dozen times in a normal immersion rinse and even spray with a hose and I still get caustic coming out the other end.

Does anyone have any tips or tricks that would help in completely rinsing this part?

Tim Hamlett, CEF
- West Palm Beach, Florida, USA
May 13, 2010

As you have experienced, caustic solutions are difficult to rinse off of a part. For this reason it is proper to use a technique called reactive rinsing, which is where you plumb waste rinsewater from a tank after an acid solution and allow it to feed your rinse tank after the caustic solution. The residual acid helps to neutralize (not merely rinse) the caustic off of the part. If you can't do that, then set up a pH controller and an acid feed to reduce the pH in your rinse tank.

Jon Barrows, MSF, EHSSC
GOAD Company

Independence, Missouri

May 17, 2010

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