Tuesday 5 April 2022

Passivating our new 304ss Stainless Steel Fermenter

In our previous blog post, we discussed the findings from our research into options and methods for passivating stainless steel. In this post, we wanted to document how we went with actually performing the passivation and a couple of things we learned along the way.

We opted to use the citric acid based version of Bar Keepers Friend powder that is available in Australia to passivate our new Cheeky Peak Nano X Fermenter, since citric acid seemed to be a safe and effective option to use to accomplish this. 

Bar Keepers Friend Cleanser & Polish powder

Firstly, we made a mixture of Bar Keepers Friend (BKF) powder and water in a glass pyrex jug to make a thick paste. We put a small amount of water in then added the powder. In hindsight, we had way too much water as we needed to use a lot of BKF powder to get the paste to the right consistency.

Our Bar Keepers Friend and water mixture to make a thick paste

You want to get the paste to a thick consistency, but not too thick. We initially had ours a little too thick, so when we tried to coat the stainless surface of our fermenter, it was clumping up and wouldn't spread easily. Thankfully the paste can be easily adjust by either adding a tiny amount of water (or more BKF powder to thicken it). 

Here's what our first attempt looked like - you can see the paste is clumpy and not spread evenly, which obviously isn't going to work particularly well

Our first attempt at applying the paste revealed it was too thick/dry and clumped up on the stainless fermenter wall

Not a big deal though - we simply added a little more water to our paste to thin it a little, then continued to apply it over the top of the clumps.

Here's how it looked after applying the paste with a more workable consistency.

Adjusting the paste consistency and it applied much more easily

At this point we left it uncovered in the garage for 30 minutes. After which point we hosed it out on the grass. 

A tip to remember for next time would be to remove all the covers/caps from any of the openings on the fermenter to let the water drain out more easily - otherwise bits of the paste tend to get trapped in these openings and have to be wiped out.

The paste rinsed off very easily with a garden hose - not wiping/scrubbing required. We then dried the fermenter with some paper towel and were left with a nice clean and shiny finish.

The final and most important step of the passivation process is to leave the fermenter open and exposed to air. It is this exposure to air that will form the passivation layer.

The end result after passivation - shiny!

The thing about passivation is there isn't really an easy way to test it at home - guess we'll just have to get a brew into it to find out, but we certainly don't expect any issues.

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