Metal finishing Q&As since 1989

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Pickling after glass-blasting

2006

We are manufacturing stainless steel frames for conveyors. St. steel is AISI 304 quality.
After welding, we want to have a good finish. And, until today we tried 3 different alternatives and came across some problems:
1) We applied grinding but we could not succeed to have a good finish. Grinding stains especially on the weldings were too visible. Could someone give me an order for grit-sizes to use for a uniform finish.
2) So, we applied glass-blasting ( 150-250 microns in metric )and we had a good finish. But, when conveyors worked in wet places, rusty stains formed all over. Yes, you can clean them off but they again form after a while.
3) And, finally, after glass-blasting we applied pickling to make st. steel regain its passive outer layer for avoiding rusty free-iron stains. But, we applied pickling for 60 mins. and the supplier of the pickling chemical ( dark purple powder ) prepared a sprayable gel and sprayed all over the surface. And, after a thorough rinsing , we observed that grinding stains became more visible, which made us repeat glass-blasting to make them invisible again.

May I have your suggestions on these topics.

Thanks.

TAYFUN YESUGEY
MAKING STAINLESS STEEL FRAMES and ELECTRICAL PANEL - Istanbul , Turkey

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Rather than to try and solved every one of your problems, I suggest you look at your blast media and or machine and rule out the possibility of media contamination. Rule out and simplify first, before solving side effects.

AF Kenton
retired business owner - Hatboro, Pennsylvania
2006