Where the
world gathers for metal finishing
Q&As since 1989


-----

Electropolishing 301 stainless steel

 

We (an autoclave manufacturer) are experiencing quality problems with electropolishing .025" thick X 7" round discs of 301 half hard stainless steel. The supplier says that water spots are the cause. The parts are blanked on a die from coil stock and then washed. The detergent is an alkaline material and is used in an industrial spray washer equiped with fresh water rinse. Composition by weight % is as follows:
5-10% potassium hydroxide
5-10% sodium silicate
10-20% tetrapotassium pyrophosphate
5-10% 4 Na ethylene diamate tetra acetate

After the parts are washed and rinsed, they are heated to 600 degrees F for one hour. The supplier claims the electropolishing operation will not remove the spots. Should the spots be removed by this process?

Tim A. Shoup
- Versailles, Ohio, USA

The answer to your question is maybe. I have seen parts where chemicals are baked in during heat treatment that were difficult to run, but not often. This is most often an oil or grease or even fingerprints. If your rinse cycle is doing its job then what you are left with is probably water spots from the rinse water. We can usually find a way to overcome these problems with relatively little effort.

John Holroyd
- Elkhorn, WI
 

---

Tim:

IF the problem is water spots it is easily correctable up front by rinsing with DI or RO water instead of tap water. The cleanliness (ion free) of your water will determine whether you have water spots. The DI may cost some money, but it is cheaper than having the problem.

Lee Kremer
Stellar Solutions, Inc.

McHenry, Illinois