Not Pickling an ASME CS Filter Vessel

[GrimesFrank]

Sorry folks but free Fe ions, suphuric acids, oxide layers etc. aren't my forte so I have a pretty basic question.

I got a vendor looking for a concession. Our spec asked for the vessel to be grit blasted and pickled......oops they didn't pickle but bead blasted only. Can we accept?

Now I would think the bead blast would accomplish pretty much what you were looking the acid bathing to do for the vessel, right? Get rid of all scale, embedded contaminants, give a "clean" surface to epoxy the outside with and provide the best carbon steel surface to resist corrosion.

Our process fluid is demin water.

Is there something crucial I'll need the pickling for here or was I over-specified (not my TS)

Frank "Grimey" Grimes
Rule 25. of Swanson's "Unwritten Rules of Management"
Have fun at what you do. It will reflect in your work. No one likes a grump except another grump.

 

[unclesyd]

I think demin water will go after the CS in most cases. We kept demin water in Al and SS until we add various additives.

Bead blasting is about the best you can do. An Acid pickle want help that much as far as paint prep unless one would use a Phosphoric acid type bath, wash primer. The only time we acid pickled CS, HCl+H3p04, was to remove mill scale from the ID of pipe.

Depending on the corrodent not much can be done to enhance the corrosion resistance of CS. The only time you will normally see a surface modification is for normal atmospheric corrosion.

 

[kenvlach]

I agree with unclesyd. Acids (preferably inhibited) are mostly to remove oxide scale.

A possible option is an ammoniated citrate 'passivation' solution, used warm. Often used to clean new boilers. You can make the solution by adding ammonium hydroxide to a citric acid solution to a pH of 9. This cleans & slightly passivates the CS until your treated demin water reaches it (if untreated, get rust water).

 

[JoeTank]

Did the bead blasting provide the proper profile for the coating system?

Joe Tank

 

[GrimesFrank]

Thanks guys,

Yes the demin water is treated.
I had a brain lapse yesterday though.....the axiom "The simplest answer is the best answer" applied.

The vessel is for a radioactive products filter. The whole unit gets disposed. Life cycle ~3 months at best. Worrying about corrosion resistance seems like having power steering installed on a go-kart.

Sorry group.

Frank "Grimey" Grimes
Rule 25. of Swanson's "Unwritten Rules of Management"
Have fun at what you do. It will reflect in your work. No one likes a grump except another grump.