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La Marzocco Linea MP-2 - water eating through stainless steel!
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dubey
Senior Member


Joined: 17 Apr 2014
Posts: 2
Location: PL
Expertise: Professional

Posted Thu Apr 17, 2014, 6:15am
Subject: La Marzocco Linea MP-2 - water eating through stainless steel!
 

Hi guys!
Fourth year of using La Marzocco Linea MP-2 (mechanical paddle) in cafe. Previous three years with no problem working on basic Faema (copper boiler and tubes).
With La Marzocco (stainless steel boiler and some of the tubes) we are experiencing problems with water which led to espresso boiler change - previous was eaten from the inside by water - leaked on seams so much we couldn't fix it.
Until begining of the year we were using regular water filtered by dedicated Brita (earlier Water+More) filters. Water was tested at 360 ppm straight from tap and 330 after Brita filtration. pH was 6.5-6.9.
No we are runing RO with bypass (bypass consists of three stages: 20 micron filtration/coal/5 micron filtration). It gives ppm of 150-180 (we can go as low as 40 ppm with RO only) and same pH.
Since RO introduction in January we had to service espresso machine once again - head groups started to leak, after disassembling parts made of stainless steel were already eaten through a bit (parts made of copper were ok...). In grup head - after removal of top element - there was reddish/rusty mud.
Do you have any ideas/recomendations for further investigations into the problem?
Iron, chloride and chlorine content testing?
Thanks!
dubey
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jonr
Senior Member


Joined: 25 Jun 2013
Posts: 298
Location: Americas
Expertise: I like coffee
Posted Thu Apr 17, 2014, 9:40am
Subject: Re: La Marzocco Linea MP-2 - water eating through stainless steel!
 

One way to corrode metal fast is to have some DC leakage current.  But I have no idea where that might come from.  

Stainless usually comes out the winner in cases of galvanic corrosion.
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dubey
Senior Member


Joined: 17 Apr 2014
Posts: 2
Location: PL
Expertise: Professional

Posted Thu Apr 17, 2014, 1:46pm
Subject: Re: La Marzocco Linea MP-2 - water eating through stainless steel!
 

Jonr, never thought of that... I'll have electrician to test for leakage.
Thanks!!!
dub
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DeanOK
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DeanOK
Joined: 24 Sep 2012
Posts: 693
Location: OK
Expertise: I like coffee

Espresso: QM Vetrano 2B
Grinder: Vario W
Posted Thu Apr 17, 2014, 6:02pm
Subject: Re: La Marzocco Linea MP-2 - water eating through stainless steel!
 

dubey Said:

Jonr, never thought of that... I'll have electrician to test for leakage.
Thanks!!!
dub

Posted April 17, 2014 link

Plug it into a GFI. If there is any current going to ground from the line voltage, it will trip the GFI, even if it is only a few milliamps.
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DavecUK
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Joined: 21 Sep 2005
Posts: 1,449
Location: UK
Expertise: I love coffee

Posted Fri Apr 18, 2014, 7:04am
Subject: Re: La Marzocco Linea MP-2 - water eating through stainless steel!
 

What is the steel being used for the Boilers 316 is the stainless of choice?
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skydragondave
Senior Member


Joined: 18 Feb 2013
Posts: 167
Location: Ontario, Canada
Expertise: Professional

Espresso: Commercial Only
Grinder: Commercial Only
Roaster: Has Garanti HG5
Posted Fri Apr 18, 2014, 7:47am
Subject: Re: La Marzocco Linea MP-2 - water eating through stainless steel!
 

If water is demineralized too much it will absorb minerals from whatever it can, including metal. Also check your pH again with the new system, you may find it acidic.
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jonr
Senior Member


Joined: 25 Jun 2013
Posts: 298
Location: Americas
Expertise: I like coffee
Posted Fri Apr 18, 2014, 10:17am
Subject: Re: La Marzocco Linea MP-2 - water eating through stainless steel!
 

dubey Said:

I'll have electrician to test for leakage.

Posted April 17, 2014 link

I had to look it up, but evidently AC leakage also causes corrosion (but needs about 100x the current for the same damage).  So I'd check for both DC and AC leakage.
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billc
Senior Member


Joined: 15 Jan 2009
Posts: 131
Location: Seattle, Washington
Expertise: Professional

Espresso: CC1 - GS - GS3 - GB5
Grinder: Baratza - Mazzer-Marzocco
Drip: My own Creation
Posted Sat Apr 19, 2014, 7:44pm
Subject: Re: La Marzocco Linea MP-2 - water eating through stainless steel!
 

When using RO are you adding anything?  The material for the boilers is either 304L or 316L depending when it was made.  The usual issue is chlorides.  While the boilers are made with low carbon stainless (L) there are still some carbon atoms present.  chlorides can interact with e carbon (I will let a chemist add the proper words) and disolve the cause the carbon atoms to go into solution.  If there is enough concentration of carbon there is a possibility it could lead to a path to the outside.  When this happens precipitates can build up and cause additional leakage. This is usually why you might see a drop of water outside of the boiler shell.  Additionally there are some problems associated with the weld area (heat affected zone or HAZ) that can cause addional carbon to be present in this area.

The stainless is not really concerned with the pH of the water or to total dissolved solid count.  It is the type of solids in the water and if there are anions present (normally in the form of chloride).


Bill
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