Oh I agree with the theory but pickling will form a passive layer.
All forms of 316 will self passivate and to an extent will 304 depending on quality and handling.
303 will rust unless chemically passivated be it with citric or dichromate. Nitric is not really a good idea with 303 unless you are very sure of the quality.
17-4 will rust and rust easily and in my experience only citric passivisation works well here. Pickling followed by by nitric passivisation will also work but the pickling will cause pitting which can result in stress cracks depending on application.
For the absolute best passivisation layer
degrease, electropolish and passivate. To me based on my experience I only
trust 316 to self passivate.
I have 100 304 components downstairs that were manufactured 3 weeks ago and put into operation pretty much straight away. They are high precision parts and are already showing signs of rusting. They were installed in a paper mill and the chemicals caused the parts to rust. I had quoted the guy €250 (minimum order) to degrease and passivate these parts after manufacture but he declined.
He rang me yesterday to ask if we could save them.
We have derouged, pickled and passivated the parts for him but I suspect they are now out of tolerance as we had to give them an extended pickle period to remove the rouge.
All forms of 316 will self passivate and to an extent will 304 depending on quality and handling.
303 will rust unless chemically passivated be it with citric or dichromate. Nitric is not really a good idea with 303 unless you are very sure of the quality.
17-4 will rust and rust easily and in my experience only citric passivisation works well here. Pickling followed by by nitric passivisation will also work but the pickling will cause pitting which can result in stress cracks depending on application.
For the absolute best passivisation layer
degrease, electropolish and passivate. To me based on my experience I only
trust 316 to self passivate.
I have 100 304 components downstairs that were manufactured 3 weeks ago and put into operation pretty much straight away. They are high precision parts and are already showing signs of rusting. They were installed in a paper mill and the chemicals caused the parts to rust. I had quoted the guy €250 (minimum order) to degrease and passivate these parts after manufacture but he declined.
He rang me yesterday to ask if we could save them.
We have derouged, pickled and passivated the parts for him but I suspect they are now out of tolerance as we had to give them an extended pickle period to remove the rouge.
