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Citric Acid, How Much to Use for Heavy Descaling

Postby vicroamer on Fri Jun 25, 2010 7:30 am

What strength should I make a citric acid solution. Boiler and pipes to be fully immersed in a bucket. I've been trawling through search results but have only found recommendations for maintenance strength solution for use in assembled machine. I have over 2kg of the stuff, which should be enough but I don't want to get into trouble by being too heavy handed with it. Also any tips would be appreciated.
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Postby frankmoss on Fri Jun 25, 2010 9:52 am

The strongest solution I ever make is 1 tbs per liter. But much weaker is sufficient for most descaling.
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Postby gscace on Fri Jun 25, 2010 11:33 am

vicroamer wrote:What strength should I make a citric acid solution. Boiler and pipes to be fully immersed in a bucket. I've been trawling through search results but have only found recommendations for maintenance strength solution for use in assembled machine. I have over 2kg of the stuff, which should be enough but I don't want to get into trouble by being too heavy handed with it. Also any tips would be appreciated.



What does the manufacturer of the descaler concentrate say? I'd follow their recs. Call em or their rep.

-Greg
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Postby frankmoss on Fri Jun 25, 2010 12:34 pm

Often people buy citric acid from a home-brewing shop, so there are no directions for making descaling solutions. In this case, the manufacturer would have no idea what concentration to use. In this case, I use OE's recommendations, which are 1 tablespoon per liter. But weaker solutions work, but more slowly.
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Postby PictureThyme on Fri Jun 25, 2010 3:30 pm

frankmoss wrote:Often people buy citric acid from a home-brewing shop, so there are no directions for making descaling solutions. In this case, the manufacturer would have no idea what concentration to use. In this case, I use OE's recommendations, which are 1 tablespoon per liter. But weaker solutions work, but more slowly.


Paul Pratt states he makes up to a 20% acid solution (sorry couldn't tell you how to measure this), with the caveat that he has years of experience restoring espresso machines.

Higher concentrations of the acid solution, not watched carefully can cause damage to delicate finishes, quickly eating through the chrome on plated brass parts. The acid can also cause galvanic corrosion where two dissimilar metals meet (http://en.wikipedia.org/wiki/Galvanic_corrosion) and quickly destroy your parts.

The steam boiler on my Linea has such a solid mass of mineral deposits in it that I opted to use a low strength solution to slowly break down the minerals. The boiler has been soaking in the citric acid solution for days. I take the tank out and scrub the crud with a green abrasive pad every day to speed the break down.

As for the other parts, I used hot water and watched everything as it steeped in the acid. As soon as the minerals were gone the part came out. The acid works more quickly with hot water than cold. Try using a cooler with the hot acid to maintain the temperature. With the steam boiler, I've been able to keep the bath water above 100F over night in the cooler.

Disclaimer: I am not an expert. The opinions stated in this transmission are strictly the opinions of the author and are probably incorrect on many levels. But they worked for me.
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Postby cannonfodder on Fri Jun 25, 2010 11:05 pm

Around two tablespoons to a liter of water is a 'normal' mix. You could go 3 or 4 tablespoons for heavier scale. When I do my every 6 months descale I use the 2 tablespoons per liter mix and it works just fine. Hot water is more aggressive so when you put all the parts in a tub to descale, put your water and citric acid powder in a bit stock pot, bring it to a low boil then dump it in your tub with the parts.
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Postby cannonfodder on Fri Jun 25, 2010 11:08 pm

Almost forgot, do not use an aluminum pot or Teflon coated. Use stainless. The acid will eat up the aluminum and may blister the Teflon. You descaling container must be able to take the heat, I used a big plastic tub.
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Postby another_jim on Sat Jun 26, 2010 1:04 am

One to two tablespoons per liter if you are flushing water through the boiler and HX without disassembling. This is the gentle treatment, used for a light coating of scale. If you are disassembling the machine, and putting the parts in an acid bath; you can remove heavy scale, and you can use a stronger acid. For this app, hydrochloric acid, aka muriatic, is normally used, at a full pH lower. If you are using citric acid in this way, you can use around 10 tablespoons per liter. You should wear the standard high school lab gear -- gloves, goggles and breathing mask -- since at this strength, it will burn skin.
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Postby vicroamer on Sat Jun 26, 2010 9:11 am

The boiler exterior has a dull grey appearance, some type of plating I suspect, I suppose that will be stripped away during the descale. Probably use 4 to 6 tablespoons per litre and see how that goes I can always go stronger if I have to.
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Postby tangje on Sat Jun 26, 2010 2:14 pm

20% would equate to 200g in 1 litre of water. That's roughly 14 TBSPs.

Vinegar, which people often use in a pinch for descaling, is 5% acetic acid.

Those numbers should help you get a sense of what people are doing.
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