Water Stain on SUS340 and SUS430

please describe color of stain and why you call it water stain.

My conjecture is that you have iron fines in your wash solutions.

milo

Hi Milo,

Thank You so much for your reply. The color is greyish and the outer lining is more prominent. it scatters all over the surface like a small dots/circles. It cannot be seen clearly with naked eyes but if you tilt the part around 45deg angle under the light, it can be seen clearly.

Well, for the name, it only comes out after washing, so we just call it water stain as we think it was cause by the Aqueous Washing.

Our washing line has now been cleaned properly. We found out that the filter has not been change for a long time thus causing this marks on the parts surface.

Thank You again...

No problem. now second question, do you/did you passivate these parts before or after washing?

milo

Yes. We do passivate the part before washing.

You could try using alkali solutions of sodium hydroxide instead, which will remove the stain and leave no discoloration.

You could try prevention which is always better than cure. There must be some halogens like chlorine, fluorine, bromine etc. in minute quantities in your water. Better switch to demineralized water which is safe.

Best of luck

Plasmaspecialist

Hi Plasmaspecialist,

Thank You so much for your help. I will try it the Sodium Hydroxide as u said.

We are using DI Water and Surfactant in our washing tank. followed by a series of rinsing plus drying.