Boiler-safe level of chlorides (and other compounds) in water

#1: Post by **JavaBuzz** » October 11th, 2015, 4:51 pm

Does anyone know if there's a generally safe level of chlorides in water that shouldn't cause corrosion in metals?
I'm particularly interested in stainless steel, being my boiler is that material (not sure what type of stainless steel).

I know I've seen here and elsewhere that below 200-250ppm sulphates is generally safe for stainless steel, but I've not seen anything related to chlorides. I do know I've found docs saying that stainless steel is much more susceptible to corrosion from chlorides than it is from sulphates (and that was alluded to earlier here as well).

This discussion was split by moderator from the topic: "Water For Coffee" book available for pre-order

#2: Post by **OldNuc** » October 11th, 2015, 6:19 pm

IIRC 20 ppm is the panic point for stress corrosion cracking in power reactors. The short answer is no Cl or O2.

#3: Post by **yakster** » October 11th, 2015, 6:30 pm

My kettles, Behmor Brazen, and my prized 1950's Faema Faemina are all stainless, so I share the concern.

#4: Post by **keno** » October 11th, 2015, 7:17 pm

JavaBuzz wrote:Does anyone know if there's a generally safe level of chlorides in water that shouldn't cause corrosion in metals?
I'm particularly interested in stainless steel, being my boiler is that material (not sure what type of stainless steel).

According to La Marzocco water specifications they recommend less than 30ppm chloride. And Synesso (see page 11) recommends zero chlorides.

October 11th, 2015, 8:06 pm

Thanks OldNuc/keno. At least with stainless steel, sounds like avoiding chlorides completely is the best/safest option.

#6: Post by **OldNuc** » October 11th, 2015, 8:34 pm

They taste bad as well.

#7: Post by **homeburrero** » October 11th, 2015, 11:39 pm

keno wrote:According to La Marzocco water specifications they recommend less than 30ppm chloride. And Synesso (see page 11) recommends zero chlorides.

+1

These recommendations are conservative. Perfectly good numbers to use if you're looking for a "safe level." In practice people might go higher than that, especially if your alkalinity and pH is reasonably high. Pentair / Claris has shared some interesting info, hosted on home-barista here: /downloads/ ... pdated.pdf That guidance is that if your alkalinity and pH is reasonably high, you're OK as long as your chloride is less than 80ppm and sulfate is less than 150 ppm. The SCAA Water Quality Handbook 2nd Ed (2011) has a section on the effect of water quality on brewing equipment where they discuss scale, but there is no mention in there of chloride or sulfate as a corrosion concern.

Also, be aware that in the common parlance of water quality discussions you need to distinguish the term chlorine from the term chloride. Chloride is the ion, Cl-, associated with common salts such as NaCl, MgCl2, and CaCl2 that are not that objectionable at moderate concentrations. CaCL2 and/or MgCl2 might be added when formulating water for coffee (GCW, for example, uses CaCL2 as a calcium additive.) Chlorine in a water spec or report is something different, refers to Cl2 gas and related chlorine compounds added as a water disinfectant. It has an odor and taste, and (according to the SCAA water quality handbook) can combine with coffee phenols to produce highly objectionable taste even at very low concentrations. So all recommendations for coffee water specify 0 ppm chlorine. Fortunately, chlorine is easily removed by activated carbon filtration.

October 12th, 2015, 1:22 am

Thanks Homeburrero!

In my initial post, I was primarily interested in the affects of adding Magnesium (or Calcium) Chloride to very low TDS/ppm water, in order to increase the GH (while also avoiding boiler corrosion, with minimal scaling).

Looks like if you have a stainless steel boiler, stainless steel is very susceptible to chloride, but it can handle sulfates a bit better. So at least for stainless steel, Magnesium Sulfate (Epsom salt) might be a better option for increasing GH (vs a chloride)? Also, for other types of boiler metals, the reverse might be true?

Looks like both chlorides and sulfates are not good tasting (sulfates maybe more so than chlorides?), but seems like the easy ways to increase GH include one or the other.

So much to think about when it comes to "Water for Coffee/Espresso".

I'm quite outside my normal domain of knowledge here, but I definitely find this interesting, and I suppose this is yet another example of why coffee can so easily become a hobby, or even more.

#9: Post by **rpavlis** » October 13th, 2015, 9:51 am

Sulphates can taste bad, but their only contribution to corrosion is enhanced conductivity so that electrolytic corrosion will be increased. This can be a problem in alloys because composition varies from point to point on a chunk of alloyed metal. Sulphate in the presence of calcium can also precipitate calcium sulphate--a difficult to remove scale. Copper and copper alloys have especially serious chloride corrosion problems.

Chloride forms complexes with many transition metals. This can (and will) dramatically increase corrosion. In addition chloride will also increase conductivity. Chloride tends to be particularly corrosive with high hydrogen ion concentration. Above a certain level it makes "briny" tasting coffee, I grew up in area with water like that. There seems to be a particular synergetic enhancement of the salt flavour when sodium is in the presence of potassium. Coffee beans are AMAZINGLY high in potassium--about 2%.

One does not like to have to "fuss" with water all the time. Some municipalities also have highly erratic water supplies that vary from fine to horrible both for taste and for corrosion. Tap water tends to contain dissolved oxygen and carbon dioxide. When heated in an espresso machine these gases are quickly eliminated almost entirely. Some complain that water not freshly drawn tastes "stale", that is either from contamination or from degassing. But in an espresso machine it is degassed by the very nature of the process.

If you do not have a plumbed in connexion, you can use a good deionising system or purchase distilled water, and add potassium bicarbonate to bring bicarbonate to about the 0.5 to 1.0 mmolar level. (50 mg to 100 mg/litre). With coffee that is extremely dark roasted there is less need for anything in the water at all. If one be careful to keep such water pure it can be stored indefinitely without problem.

Once I deliberately brewed some espresso and added NaCl to it just to test. It tasted like the nasty coffee of my boy hood! The beans have some chloride, (about 0.05%) and much more at all is bad for flavour. (By the way, that is one of the reasons needs to clean up every thing after making espresso.)

October 14th, 2015, 12:22 am

Thanks for the contribution, rpavlis. Some very detailed information too.

This is off the chloride topic, but any reason potassium bicarbonate seems to generally be recommended over sodium bicarbonate (when trying to increase pH/KH and such)? A little better taste possibly? Maybe a combination of the two could compliment each other?

EDIT: Slightly updated the topic header/subject now to reflect this.