Rust on stainless HERMS coil

[desitter]

G'day,

Just put my new 3 vessel HERMS system (modeled of the electric brewery) through a test run today, using only water. After having the coil submerged in water within the HLT for approximately 4-5 hours, I drained the HLT to find what looks like rust spots all over the coil, and a few on the bottom of the stainless HLT pot itself. There was also a discolored ring that had formed where the water level had been, and I could have sworn the water had taken on a green tint. Does anyone know what's gone wrong for this to happen, and what I may do to remedy it? This was the first time the element had been used.

Cheers,

 

[Danscraftbeer]

There's some more knowledgable people here but was it all washed prior? The green tint must be chemical somehow. A treatment for selling apearance etc? Stainless steel is only resistant of staining and rust. The only way to remedy is the higher pollished the surface the more its resistant but I wouldnt like to try and pollish that coil. Its dissapointing when this happens and it probably comes down to the quality of the steel. I have an imersion chiller that is not at all pollished. Its been through hard boils and not a single hint of any stain.

 

[desitter]

Hi Dan,

No the element and coil were as they were when I purchased them. I had not rinsed/cleaned them yet (planned to as part of this wet testing). So you might be right that the green tint and discolouring may have come from something on the element. If it is the coil's metal I'm going to be pretty pissed, as I paid $$$ for it shipped from the states. I'll see if anyone else has any ideas before using a little elbow grease and bar keepers friend.

 

[QldKev]

I'd be talking with the supplier

 

[Feldon]

Possibly the coils have rubbed against each other during transit? Or have you been banging around in there with a metal spoon?

Stainless steel is an alloy containing metals like chromium and nickel, but its mostly made of iron. If stainless gear gets rubbed against itself iron particles can impregnate the surface. This stuffs up the alloy composition by creating too much iron concentrated in a localised spot, and that spot can start to rust. If left alone a chain reaction can start and the rust can continue to penetrate deep into the stainless.

Right now its probably just superficial surface rusting. A good rub down with Bar Keepers Friend should fix it. A soak in a strong citric acid solution might also help. But something acidic, even Star San is better than nothing (others will tell you to use Nitric Acid but avoid it like the plague unless you've handled it before - nasty stuff).

 

[desitter]

The rust appears to be on both areas in contact with the other parts of the coil, and areas that are not. The coil has sat by itself indoors for about 6 months before it was installed, and was really only handled minimally for sizing and installation (simple process of sticking it in the compression fittings and tightening). I find it really strange that I would see so much rust appearing in such a short time period in water. I sent the supplier an email, so we'll see what they have to say.

 

[Danscraftbeer]

Also play the devils advocate. In hindsight. Wash/scrub everything with apropriate solutions prior to using them. I always have, you never know what residues of chemicals are on anything manufactured. Pre washing is the recomendation of producers of products like this anyway.
It could be a simple as some chemical reaction maybe with your treated tap water.

 

[wessmith]

You didnt use steel wool to clean the s/s by any chance? In any case, as others have suggested get an acid solution (citric or preferably phosphoric) and a genuine green scotchbrite scrubby and start polishing with that. Let the vessel and coil soak in the solution for an hour or so before starting the polishing.

Wes

 

[H0U5ECAT]

Stainless comes in many grades.
http://www.atlassteels.com.au/site/pages/stainless-steel-datasheets.php
Generally, you should be using 316 as it is preferred in a wide variety of uses in commercial kitchens, however the Australian standards state that the minimum to use is 304.
But... 317 will give you the best resistance to corrosion.

Remember that stainless isn't fullproof. It comes down to handling and preparation.
cellulose can stain/mark 304 unless the temperature is kept low.
Fats and fatty acids only affect grade 304 at temperatures above 150 deg C, and grade 316 above 260 deg C, 317 is unaffected at all temperatures.

Go here for some cleaning and handling tips.
https://en.m.wikipedia.org/wiki/Stainless_steel#Maintenance_of_stainless_steel

Any staining or spotting, especially on mill finish stainless (unpolished, looks as if it came straight from the foundry) can be removed with a slight acidic wash and a scourer.
Vinigar, citric acid etc, all light household acids found in your pantry will do this.
Sulfuric or hydrochloric acid can be used, but its a little more nastier and care must be taken in using and disposing of. I would only use it in the harshest of situations.

Did your supplier tell you what grade you have? Or did you throw caution to the wind and buy it as cheap as possible from aliexpress?

 

[MastersBrewery]

I've had this problem with my ss immersion chiller, and it seemed to be from when the coil was being formed. That is to say the tools used to form the coil were mild steel, leaving marks randomly along the length of the coil. I got out the scotch brite and went over the whole thing. I haven't noticed it's return since. I'd go with some of the advice above, give it a good clean with bar keepers friend and a scotch brite and you should be good. ( I now do this with all new ss I get before installing )

MB

 

[zeggie]

Was it cleaned with a wire brush or something? Was any holes cut in the pot for the coil?

Could be a few things.

If you punched/cut a few holes in the pot there could be flakes of metal in there. Always a good idea to do a good soak and long rinse in starsan to passivate.

A good scrub with a NON-metal scrubber and some barkeepers friend, the a good rinse with starsan will probably fix it.

 

[desitter]

Thanks for all your comments and suggestions guys,

The supplier says much the same. I needed to clean and passivate before using it. No steelwool or wire brushes where used, likely there was still oil/soil load present that was preventing it from passivating in contact with air. This was removed while in the water, exposing the surface underneath. I have some green scotch-brite's and bar keepers friend, which I'll use to thoroughly clean it, then soak in a 5-10% citric acid solution at ~65C for 30 mins just to be extra thorough. I have a couple of brewbuckets coming which I need to passivate as well, so I may as well just do them all the same way.

Thanks again,
Cheers

 

[pist]

You can get surface rust on stainless from rubbing against mild steel, tooling when being formed, and even just from grinding sparks if a standard carbon steel is being ground near it...or if you use a grinding disc or flap disc that has been used on standard steel. Rub it back with a non metal scourer or a fine grit sandpaper and passivate it now before it goes deeper than the surface

 

[fraser_john]

Like others have said, minor rust probably caused by the tools forming the coil, scrub it off with stainless scruby or a plastic one. If using water in the herms, add a cap full of vinegar to keep it acidic, or, just use the cheap glycol from Super Cheap Auto, I use it an just leave it in there.

 

[klangers]

Stainless needs to be passivated or "pickled" before use. Get some concentrated acid (eg no rinse sanitiser) and paint over the surface. Leave for 5 minutes and then rinse away.

This is to ensure that the protective chromium oxide layers have been built up. What happened is that this had not taken place before water came into contact with the steel.

 

[desitter]

Took about an hour, but I was able to get into every nook and cranny and remove all of the surface rust with Bar Keepers Friend. I followed this with a rinse, then an extra wash with Trisodium phosphate, another rinse, then transferred the 1 oz to 1 gallon StarSan solution I used to passivate my two BrewBuckets (not sure why I made two lots of solution now that I think about it). Left for 20mins, drained, then let air dry before rinsing with water and letting air dry again. So hopefully that fixes the issue. Again thank you to everyone who commented. I'll be sure to post a follow up to let you all know if I was successful in preventing further corrosion.

Cheers,