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Old 10-19-2013, 12:54 AM   #31
403Brewer
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So basically no avoiding this unless you have some kind of plastic or ceramic...brass won't solve the problem?

 
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Old 10-19-2013, 10:34 AM   #32
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Quote:
Originally Posted by Stealthcruiser View Post
With dissimilar metals and moisture,you'll always have corrosion, just some quicker and more aggressive than others.

This is true to an extent. However this generally won't happen unless you keep liquid in your equipment for long periods of time. Especially with Copper up against Stainless steel.

Here is a chart to help. http://www.engineersedge.com/galvanic_capatability.htm

For normal conditions, you want to keep the anodic index value less than .25V difference between the two metals in contact. Copper is .35V and Stainless(304 SS) is .50V (18% chromium-thus 18/8 SS). You still would need a conductive path(Water/Wort) to move ions from one metal to the other.

 
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Old 10-19-2013, 08:04 PM   #33
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So an easy solution is just unscrew the dip tube post boil until you're ready to go again

 
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Old 10-21-2013, 01:05 AM   #34
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Quote:
Originally Posted by MachineShopBrewing View Post
This is true to an extent. However this generally won't happen unless you keep liquid in your equipment for long periods of time. Especially with Copper up against Stainless steel.
The key for us, if I understand this right, is the length of exposure. Short-term exposures (such as a 1 hour boil or 1.25 hr. mash) reduces the rate of corrosion.

And the next question is, so it corrodes a little. What harm is there in it? Does this minimal corrosion release anything harmful? If it does, is it at a level that we need to be concerned about it?

Doesn't a lot of this concern originate from a time when roofers used to stuff a bunch of galvanized nails in their mouths and did it day in and day out? The proportion of exposure is, IMO, significantly different.
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Old 10-21-2013, 04:44 PM   #35
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Quote:
Originally Posted by Puddlethumper View Post
The key for us, if I understand this right, is the length of exposure. Short-term exposures (such as a 1 hour boil or 1.25 hr. mash) reduces the rate of corrosion.

And the next question is, so it corrodes a little. What harm is there in it? Does this minimal corrosion release anything harmful? If it does, is it at a level that we need to be concerned about it?

Doesn't a lot of this concern originate from a time when roofers used to stuff a bunch of galvanized nails in their mouths and did it day in and day out? The proportion of exposure is, IMO, significantly different.

I wouldn't worry even long term exposure with copper against stainless. The two metals are so close on the galvanic scale that you won't see any corrosion unless in a very tough environment.

It helps to also hit your stainless and copper with a strong mixture of star san and let it air dry. This will re passivate the metals creating a passive oxide layer to protect them.

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Old 10-22-2013, 02:44 PM   #36
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Quote:
Originally Posted by MachineShopBrewing View Post
I wouldn't worry even long term exposure with copper against stainless. The two metals are so close on the galvanic scale that you won't see any corrosion unless in a very tough environment.

It helps to also hit your stainless and copper with a strong mixture of star san and let it air dry. This will re passivate the metals creating a passive oxide layer to protect them.
Super! I'd heard of passivating stainless but had no idea a simple StarSan bath would do it. Thanks!

So what about brass and stainless? Any issues there? Same solution?
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Old 10-22-2013, 06:39 PM   #37
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I wouldn't worry about brass and stainless either.

 
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