Identifying this problem

[Gbbc]

Hi, can someone help me to identify what these stains are? After a 30 min. caustic and a 60min Nitric/phosphoric CIP I end up with this. If you look closely, ignoring that rainbow effect, you will see a brownish film on the shell which you can scrape off. This is the same for my mash tun and kettle. How do I get it spotless? Should I be worried about this?

[NHBrewer23]

It looks like mineral deposits. I would try running a caustic cycle with an oxidizer additive. Before switching to an acid cycle, try and spray the trouble areas with a garden hose. The gold film should peel off in chunks with the water pressure. You may need to hit the areas with a brush in between cycles. Once you have adequately rinsed after the caustic, cycle your acid for 15-30 minutes. Hopefully it will take care of the build-up and staining. If not, try contacting your chemical supplier. They should be able to assist.

[andrew_FSBC]

Looks just like the grist hydrator in my Premier system. An hour recirc of 160° PBW every few weeks gets it spotless for me. Sometimes you have to hit it with a brush too.

[kererubrewing]

We use Sodium Percarbonate (main component in PBW) at a rate of 5g/L as an additive to our usual caustic treatment. Our stainless comes up very shiny every time.

[Gbbc]

Thank you all for the replies. Sorry it took so long to get back to you, wanted to sort this out first. After trying everything from PBW (VERY expensive in Australia) to cheaper local products containing sodium percarbonate, nothing worked as good as 3% sodium hydroxide with 0.7% v/v hydrogen peroxide.

Kettle and mash tun spotless without any manual scrubbing.

Cheers

[Ted Briggs]

ignoring that rainbow effect, you will see a brownish film?

Don't ignore the rainbow- that's telling you its a protein/organic soil. So your solution of caustic cleaning with a proxy booster was right. I would back it off in steps and see if less caustic will work. 2% should usually be enough.