A reason for draining small boilers
- espressme
- Posts: 1406
- Joined: 18 years ago
There are often posts from folks wondering about whether draining small boilers is necessary. It may not be but leaving water in a brass or copper boiler that has elements containing other metals for a long time is not a good idea. Galvanic corrosion would be the correct term for a problem caused by such a situation. Which means that two or more dissimilar metals in an ionic solution will make a battery. That battery will transfer metal from one surface to a surface of a dissimilar metal.
I just had a question by a friend about little tiny pits/ pin holes through the boiler. Mogogear had a similar problem when he rebuilt the "Oly Twins."
I think that the problem may be caused by an acidic, or base, or salt, ionic concentration of the water. That would be caused by the water being boiled off and chemicals in the remainder becoming more concentrated. The pitting is a electroplating artifact that deposits the brass/copper from the closest points of the boiler onto the dissimilar metal sheath of the heating element. If there were a slight current leakage of the element or a voltaic potential established, it would make the problem worse. Heat also quickens a reaction. Since this effect is often found when rebuilding machines with bad heaters, there may also be a correlation.
I have found a similar problem in silversmithing where the acid solution used to remove flux and tarnish will copper plate everything in the solution when a bit of iron is introduced into the solution.
my 1¢
-Richard
I just had a question by a friend about little tiny pits/ pin holes through the boiler. Mogogear had a similar problem when he rebuilt the "Oly Twins."
I think that the problem may be caused by an acidic, or base, or salt, ionic concentration of the water. That would be caused by the water being boiled off and chemicals in the remainder becoming more concentrated. The pitting is a electroplating artifact that deposits the brass/copper from the closest points of the boiler onto the dissimilar metal sheath of the heating element. If there were a slight current leakage of the element or a voltaic potential established, it would make the problem worse. Heat also quickens a reaction. Since this effect is often found when rebuilding machines with bad heaters, there may also be a correlation.
I have found a similar problem in silversmithing where the acid solution used to remove flux and tarnish will copper plate everything in the solution when a bit of iron is introduced into the solution.
my 1¢
-Richard
richard penney LMWDP #090,
- another_jim
- Team HB
- Posts: 13942
- Joined: 19 years ago
Galvanic corrosion is a well known problem in Gaggia home machines, with their incomprehensible choice of using a half aluminum, half brass boiler. However, stainless steel to brass couplings, e.g. as used on pump lines, have virtually no galvanic potential.
In quality espresso machines, steel and brass are the only two materials used; and it seems inconceivable that an Olympia machine would use aluminum couplings. So I'm wondering if galvanic corrosion is really the culprit.
In quality espresso machines, steel and brass are the only two materials used; and it seems inconceivable that an Olympia machine would use aluminum couplings. So I'm wondering if galvanic corrosion is really the culprit.
Jim Schulman
- espressme (original poster)
- Posts: 1406
- Joined: 18 years ago
Hello Jim,
You do have a point. I am really looking for answers as a way to clear my mind of the problem.
I just wonder why it seems that it is only the Olympia machines that exhibit this odd boiler pin holing at the level of the heater element.
Gremlins assuring the level of their bath water???
Only different thing I have noticed is that the Oly boilers have the element also silver brazed to the base above the resettable overtemp switch for a quicker shutoff.
Clueless in Menomonie
-Richard
You do have a point. I am really looking for answers as a way to clear my mind of the problem.
I just wonder why it seems that it is only the Olympia machines that exhibit this odd boiler pin holing at the level of the heater element.
Gremlins assuring the level of their bath water???
Only different thing I have noticed is that the Oly boilers have the element also silver brazed to the base above the resettable overtemp switch for a quicker shutoff.
Clueless in Menomonie
-Richard
richard penney LMWDP #090,
- shadowfax
- Posts: 3545
- Joined: 19 years ago
Richard, I googled "copper pitting" and my first hit was this EPA study that talks about problematic pitting in copper piping in high-pH, low alkalinity water, seemingly void of galvanic corrosion--looks like they found chloride as a major culprit?
I wonder if you couldn't just put a pinch of baking soda in your water, as Jim suggested w/ galvanic corrosion in Gaggia boilers, and basically crank up the alkalinity of the water you're using and avoid pitting altogether? At the very least, it's probably worth testing your input water to see what kind of alkalinity/pH you're getting to see if it's cause for concern.
I wonder if you couldn't just put a pinch of baking soda in your water, as Jim suggested w/ galvanic corrosion in Gaggia boilers, and basically crank up the alkalinity of the water you're using and avoid pitting altogether? At the very least, it's probably worth testing your input water to see what kind of alkalinity/pH you're getting to see if it's cause for concern.
Nicholas Lundgaard
- another_jim
- Team HB
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In a sealed boiler, I guess the chlorine will not dissipate as it does in standing water. So if chlorine based corrosion is the culprit, it could happen in an espresso boiler. With the Oly, or other manual fill machine, it would mean a carbon filter is a good idea.
Water at pH of 9 with low alkalinity That's kind of hard to swallow either literally or metaphorically. Perhaps the implication is that with something like pH 8 water, the same thing can happen, only more slowly.
If the carbonate alkalinity is low, the high pH they cite is coming from some non-carbonate alkali. in essence, I think the study says that if there's enough chlorine ion the water to turn it into dilute bleach, it will pit copper.
Water at pH of 9 with low alkalinity That's kind of hard to swallow either literally or metaphorically. Perhaps the implication is that with something like pH 8 water, the same thing can happen, only more slowly.
If the carbonate alkalinity is low, the high pH they cite is coming from some non-carbonate alkali. in essence, I think the study says that if there's enough chlorine ion the water to turn it into dilute bleach, it will pit copper.
Jim Schulman
- espressme (original poster)
- Posts: 1406
- Joined: 18 years ago
I shall leave this thread open and thank all who have given the information. It would seem that, with water left in a boiler over a long storage that some chlorine in the water, from whatever cause, may be strong enough to cause pits in copper alloys.
The suggestion from Jim to use a carbon filter to remove all such chemicals from the water before putting it into the boiler seems the best fix for a small machine. Since I have used a home carbon filter pitcher and change filters every couple months, it would seem that any short term problem for my machine is solved.
I would also assume that draining and rinsing the boiler before any period of non-use would be a worthwhile action. Allowing the boiler to dry after the rinse could be a plus. Remember also that there may be water trapped above the piston in some machines.
Thanks Again!
-Richard
The suggestion from Jim to use a carbon filter to remove all such chemicals from the water before putting it into the boiler seems the best fix for a small machine. Since I have used a home carbon filter pitcher and change filters every couple months, it would seem that any short term problem for my machine is solved.
I would also assume that draining and rinsing the boiler before any period of non-use would be a worthwhile action. Allowing the boiler to dry after the rinse could be a plus. Remember also that there may be water trapped above the piston in some machines.
Thanks Again!
-Richard
richard penney LMWDP #090,