Hi Folks,

I'm posting this as its own topic so it will be more visible and invite discussion.

I just bought a used Microcimbali and caught a post that another member here got a similar machine. But he was less fortunate than me and discovered his aluminum boiler had corroded to the point it can't be fixed. A discussion started on that thread about how to maintain and clean aluminum boilers. See: Newly acquired Microcimbali Liberty: had a few restore questions Here's a summary of the aluminum boiler issues discussed there:

1. Aluminum boilers can corrode and die
2. Doug Garrott (orphanespresso) advises to chrome plate aluminum boilers if you want one to last long
3. Another poster says both aluminum and chrome can oxidize, so this may not be a solution
4. If you empty an aluminum boiler, does it still oxidize in humid air?
5. If your aluminum has oxidized, do you want to descale? Or, would descaling remove the oxidation that can serve as a protector against further oxidation. In that case, would you remove extra scale with a wire brush?

I followed the instructions on the Microcimbali base and emptied the water in my other aluminum boiler machine. I recall aluminum window frames that corroded on the outside, not the inside, and I guess this is because only the outside was exposed to rain.

I'll add another consideration.

6. Does consuming water heated in aluminum create an increased risk of dementia? The topic is controversial because I've seen online articles that the plaques in Alzheimer's patients can form around aluminum oxide and other, later articles that say no sufficient link has been made between using aluminum in cooking and developing Alzheimer's Dementia -- I'm not a physician or researcher, so this is only a consumer-level reference. (I don't know that cooking in aluminum needs extensive discussion considering how little water one may consume from an aluminum espresso machine.)

Your thoughts?

Before I discovered that my boiler was beyond repair my plan was to have it anodized. For me the benefits were corrosion resistance and also I could get color anodizing to give it a more personal touch. From previous anodizing experiences the main difficulty with doing this to a microcimbali boiler would be the boiler dissasembly down to only the aluminum and also the boiler making it through the prep process before the actual anodizing. Another thing to keep in mind is that this type of process can add some thickness which might affect reassembly.

I type this post while enjoying some Redbird espresso from my Gaggia Classic and wondering what type of scale buildup is currently growing in my boiler after 5 months of use.

As for the repairs Im of the mind that anything can be repaired. Ive only seen generalized pics of the Microcimbali so its tough to get too many ideas without seeing one in person. Too complex to install a liner or sleeve of some type?

Any other high tech food safe coatings?

If it is a aluminum casting could a casting be done in brass?

Many possibilities; its just a matter of how much time/money/effort its worth?



Anodizing is just an accelerated/controlled corrosion leaving a thick layer of aluminum oxide, doesent add much if any thickness and does offer some corrosion resistance.

There are some good how to articles on anodizing online, its basicly a DC power source and a weak caustic souition (usually sulfuric acid)

Adam:

That anodizing idea is really interesting. Here's a web site I found describing the process. It seems too expensive to set up at home unless there are many parts to anodize, but this gives a really good idea of what is involved, and it's a good way to add color, too. Is it food safe?

http://www.focuser.com/anodize.html

Aluminum gives up its electrons/atoms quite readily, as compared to other metals. If you have ever owned an ocean going boat, you'll be familiar with "zincs", which you attach to aluminum parts that are submerged in the ocean. This is because the salt water acts much like the electrolyte in a battery and the aluminum is happy to give up its electrons and corrode. The zinc (which is even more happy to give up its electrons/atoms), act as a sacrificial lamb of sorts, thus saving your valuable aluminum parts on your boat.

Anyway, so if you are making coffee and aluminum is involved (and heat), I would be careful. It wouldn't be my first choice. In fact, with my La Pavoni PID project, I was originally going to use an aluminum rod to attach the RTD sensor to. Since aluminum transmits heat faster than bronze, I figured it would be more responsive. Then I thought again and decided to use brass instead (and then changed to stainless).

As far as your boiler goes, I think hard chroming might not be a bad idea. I think some boilers are nickel plated aren't they?

Ray

As far as I know the anodizing is food safe once completed.(as safe as the aluminum I guess) The anodized surface is much more durable than the aluminum itself (aluminum oxide)
I know if you tig something thats been anodized you can actually see the aluminum underneath the oxidation melt before the oxidized surface.

Lots of aluminum cups and cookware are/were hard anodized.

I looked into it for doing some AR15 recievers I was machining.

Personally the idea of aluminum anything involved with cooking/drinking never sat well with me. We had those aluminum cups when I was a kid and I always thought they had a funny taste.

As for the plating idea, I wonder if copper plating would hold up, thats also a process that isnt too far out of the reach of a serious hobbiest, as well as nickel plating

Before seeing the latest posts (including Ray's above where he makes the same suggestion), I asked Lucio Del Piccolo (H-B member Lvx) whether there is a solution to the corrosion of aluminum and he suggested* adding a zinc bar to the water for the same reason. The zinc acts as an anode, corroding instead of the aluminum. As in a battery, zinc, a less noble** metal than aluminum, loses electrons that migrate to the aluminum (acting as cathode), creating a small current. Neither he nor I know about food safety of this and Ray has hesitations too, but zinc is a common mineral supplement, although it isn't necessarily pure zinc (the one I take is zinc gluconate).

From the link on anodizing I inserted above, a nice aspect of anodizing is that you can apply color because the material is porous.

ANeat wrote: The anodized surface is much more durable than the aluminum itself (aluminum oxide)

Apparently in the anodizing process the surface of the aluminum goes through two changes. First it becomes aluminum oxide. Then it becomes aluminum hydrate, which is much harder.


* Lucio referenced an article online written in Italian and forwarded me the automatic translation: Sporeni, A. "Alumino: La corrosione non è una fatalità." Downloaded yesterday from http://www.calypsomusic.org/DOCUMENTI/A...osione.doc

** As I understand it a "noble" metal is less vulnerable to corrosion compared to one that is less noble or "base."

At the very end of Jim's water faq, there is a section about Gaggia (Al) boilers, worth a read for you, if you haven't seen it.
http://www.big-rick.com/coffee/waterfaq.html

As far as safety is concerned, I remember reading a long time ago that the biggest source of Al for most people was antiperspirant. It contains Al, and is readily absorbed into the large pores under your arms.

If the following article is correct, Al does not absorb easlily through your digestional tract, but does through skin
http://www.controlyourimpact.com/articles/antiperspirant-aluminum-and-alzheimers-disease/

Randy

randytsuch wrote:At the very end of Jim's water faq, there is a section about Gaggia (Al) boilers, worth a read for you, if you haven't seen it. <clip>

Thanks Randy: For those who don't want to read the whole FAQ, one of Jim's main suggestions for aluminum boiler machines is completely flushing the boiler after each espresso brewing session. This makes me wonder if inserting a zinc bar in the boiler would be easier.

Thanks also for the reference that states very little aluminum is absorbed during cooking.

I did some online research about zinc as a dietary supplement and came upon this article on the NIMH site: http://ods.od.nih.gov/factsheets/Zinc-HealthProfessional/ .

In addition to zinc being required for healthy functioning, one can overdose on zinc, but from the article I would guess that's a larger amount than would be absorbed from zinc kept in a Microcimbali boiler. But the article reminded me of another issue with zinc, which probably explains why it isn't commonly put in espresso machines. After all, if we amateurs are pondering its use, wouldn't espresso machine manufacturers consider it too? When taking zinc lozenges for a cold, I can barely taste a thing for many minutes afterward. I'll live dangerously and order up some zinc and report back whether it has that same effect in a boiler.