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"Trouble rinsing small dia tube with one end closed (for black hardcoat)"


We are running a job:

Hardcoat .0005" - .0008" thick, dyed black
Alloy: 6061

The part is:

Tube 5/8" OD x 5/16" ID - CLOSED ON ONE END
The part has a tab with a hole at one end which we rack in
The total length of the part is 4"
The hollow portion is 3" long

The part requires very careful handling & rinsing & needs partial inside coating (visually coated).

The problem is:

- we rack the parts horizontally & tilt our hoist after each tank for rinsing.
- After each tank we find that even with tilting our hoist to a sharp angle for drainage, the parts still hold a lot of solution inside of the tube, due to "surface tension"
- Currently, to fix this, after every tank, we go to a staging area & my tank men physically pick up the racks, & give them a quick shake & that is where the majority of the solutions are coming out.
- Anyone have a better idea or suggestion on how to deal with this draining / rinsing problem?

David A. Kraft
- Long Island City, New York


David, if you add a rinse aid (wetting agent) to the rinse water, lowering the surface tension, more of the water will drain out of the tubes. If you need a source of the rinse aid, let me know.

Roy Nuss
Trevose, Pennsylvania, USA


Hi Dave,

I would have thought that your company would have come across this problem years ago. Two thoughts-1. Hit it with a rapid movement of high pressure air at probably a 45 degree angle to the tube. Long enough to work, but not so long as to dry the tube 2.Run a gloved had across the opening of the tube several times. Any possibility of attaching a vibrator to the flight bar?

James Watts
- Navarre, Florida



We, too, have run parts very similar, and run across the same issue. To my knowledge, you are handling it the best way. Our spray rinsing wasn't adequate enough to insure that all parts were completely flushed. Hope you factored that extra labor in when you quoted the job! Perhaps the copper-iridium coin.......

Hey James,

I didn't understand your comment about rubbing a gloved had across the mouth of the tube? We tried the air blast.. but when you have several hundred tubes on a rack, it got a little messy, and it was more time consuming.

Marc Green
Marc Green
anodizer - Boise, Idaho


Hi Mark,

Running your hand across the bottom of the tube changes the effect of the surface tension and allows the solution to run out. It takes 2 or 3 passes across a 1/4 " tube to get it all out except a trace on the rim. You are right, air is messy. We cheated and used high pressure air (OSHA would not have approved) They are all time consuming, including taking it back to the load station to shake it. On deep blind holes, we literally manually flushed each hole with a very fine jet of water. Modified an air hose with a plastic tip. Used full tap pressure. Yes, we charged accordingly, but the customer had no choice as we were the only shop that would do it to his satisfaction.

James Watts
- Navarre, Florida

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