plating, anodizing, & finishing Q&As since 1989
Dull Stainless Steel After ElectropolishingˇÜ³.But I Want it Shiny!
I am having huge problems electropolishing some 304 stainless steel wire. We use a Phosphoric, sulphuric acid bath and usually the wire is very shiny and highly reflective.
Using a new batch of wire, the surface is dull and on closer inspection much preferential etching is occurring. Have tried changing the current to see if this changes things, but unfortunately it doesn't.
Is there a problem with the bath (which appears to be electropolishing other parts quite well) or with the wire material?
Is there something I may be able to add to the bath to aid in forming a surface that isn't dull?
Thanks in advance.Kayte Worrall
- Melbourne, Australia
Two common causes of etching are:
- Insufficient current--you have to cross over the hump and get from the etching range to the electropolishing range. Is there any chance that this "new batch" is larger diameter wire, and even though you have increased the current, you haven't increased it enough?
- Water in the solution. But if you are still satisfactorily electropolishing other parts in the same bath, this is unlikely to be the problem.
Sound like the wire, but I don't really know what spec you would insist on. Hopefully, someone else can offer further advice.
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
If the same solution is being used to polish other items and they are OK, are you using a separate rectifier for the wire process? Then that could be the cause, possibly a phase out ? Over temperature could be another possibility.
John Tenison - Woods
- Victoria Australia
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