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ZEBRA LINES ON HARD ANODISED COOKWARE

IN SOME LOTS, WHILE DOING HARD ANODISING ON COOKWARE, WE FACE PROBLEM OF ZEBRA LINES. EVEN IN THE SAME BATCH, FEW PIECES ARE OK AND FEW GETS REJECTED. WHAT IS THE CAUSE AND HOW TO AVOID THE SAME ?
MOHAN BHOGLE

2006

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2006

We will need more information in order to serve you a more definitive answer.

Alloy? Brief description of your process.. (Desmut Time) especially

How do the parts look before you start to HC them? Are the impurities visible at that point in time?

How do the parts appear out of the Etch? can you see the lines at that point?

How do the parts appear out of the Desmut? can you see the lines at that point?

Have you tried Deox/Desmuting BEFORE etching?

Sounds carbon based in the alloy to me. But with the lack of information you have provided it could possibly be anything.

Ryan Cook
Toccoa, Georgia

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Mohan

Look at your contact/rack points. They might not be secure enough.
Willie Alexander

2006

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alloy : 3003, desmut time : 5 minutes,
lines visible after dismut. we feel it is because of rolling mistake in aluminium. kindly guide.
MOHAN BHOGLE

2006

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3XXX series aluminium is notorious for being rich in Manganese. I would titrate out your Deox/Desmut and make sure it is up to par. 5 minutes does not sound long enough of a cleaning time for the problem you are facing. Try 10 minutes desmut time first, If it does not work try making up a fresh Desmut in a 5 gallon bucket and try desmutting the part in here before Dumping the entire bath.

It is possible to have Iron or another contaminant embedd itself into the part while it is machining. It depends on what the tooling you are using is made up of.

I think the desmut is a good place to start.

What type of Desmut are you currently using ? (possibly just Nitric and not a Blend?)

Ryan Cook
Toccoa, Georgia
2006

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2006

DEAR RYAN,
THANKS FOR YOUR REPLY. THE PROBLEM IS FACED ONLY WHEN WE DO SATIN GLOSS FINISH AND NOT WHEN WE DO matte finish. ALSO IN DEEP DRAWN ITEMS THE PROBLEM IS NOT THERE. ONLY IN ITEMS WHERE THERE IS NO DRAWING SUCH AS CONCAVE GRIDDLE THE PROBLEM OCCURS. ALSO IN ITEMS SUCH AS FRY PANS, WHERE THE WALLS ARE STRETCHED AND THE BOTTOM IS NOT STRETCHED, THE PROBLEM OF ZEBRA LINES OCCURE ONLY ON THE BOTTOM. THE WALLS COMES OFF FINE. THERE HAS TO BE SOME RELATION BETWEEN STRETCHING OF ALUMINIUM IN PRESSING OPERATION AND ZEBRA LINES.
I AM WAITING FOR YOUR VALUABLE FEEDBACK ON HOW TO OVERCOME THE SAME.
THANKS & REGARDS,
MOHAN BHOGALE

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2006

DEAR RYAN,
THANKS FOR YOUR REPLY.
WE ARE FACING THIS PROBLEM IN ONLY ITEMS WHERE DRAWING IS NOT DONE IN PRESSING SUCH AS CONCAVE GRIDDLE. IN DEEP DRAWN ITEMS LIKE SAUCE PANS, DUTCH OVENS THIS PROBLEM IS NOT SEEN. ALSO IN FRY PANS, SOMETIMES WE HAVE THIS PROBLEM ONLY ON THE BOTTOM OF THE PAN AND THE EDGES COMES OFF FINE. THERE HAS TO BE SOME RELATION BETWEEN DEEP DRAWING OF ALUMINIUM AND ZEBRA LINES. PLEASE ADVISE.
THANKS,
MOHAN BHOGALE