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Sailboat Owner's Guide to Corrosion - Basic Theories (Collier 1-4)

Feb 14, 2014
5,560
Hunter 430 Waveland, MS
The confusion in terms is mixing chemistry involved.

Example is Sodium Chloride.

When not in water or dry, is a crystal [does not pass an electrical current]

Put NaCl in water, it dissolves to form an Electrolyte. [Or will pass an electric current]

Na [-1] + Cl [+1] + H2O

So we need the Electrolyte to be part of the Galvanic Corrosion Electrochemical Circuit.

Jim...

PS: Distilled water has no electrolytes and will NOT pass an electric current.
 
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Oct 19, 2017
6,850
O'Day 19 Littleton, NH
PS: Distilled water has no electrolytes and will NOT pass an electric current.
So water is not conductive, as we were taught in school. Conductivity comes from the dissolved material, salts, metals? There's a lot of iron in my well water. Does that make it an electrolyte?

-Will (Dragonfly)
 
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dLj

.
Mar 23, 2017
1,758
Belliure 41 Snug Harbor, Lake Champlain
So water is not conductive, as we were taught in school. Conductivity comes from the dissolved material, salts, metals? There's a lot of iron in my well water. Does that make it an electrolyte?

-Will (Dragonfly)
Water becomes conductive through the ions that are dissolved in it. So sure, you likely have an electrolyte...

dj
 
Mar 26, 2011
2,909
Corsair F-24 MK I Deale, MD
So water is not conductive, as we were taught in school. Conductivity comes from the dissolved material, salts, metals? There's a lot of iron in my well water. Does that make it an electrolyte?

-Will (Dragonfly)
In fact, there is very little iron in the water, depending on the pH. No more than a few ppm. What you see is precipitation when ferous oxidizes to ferric. Even in well water, it is tiny compared tothe contributions of sulfate, bicarbonate, chloride, sodium, and calcium.

I've always found these plots useful.


 
Oct 22, 2014
15,695
CAL 35 Cruiser moored EVERETT WA
With such small amounts of FE in the water is is a wonder our tastebuds allow us to taste the iron when we drink the water.
 
Feb 14, 2014
5,560
Hunter 430 Waveland, MS
Since blood chemistry requires Fe to attach Oxygen, @Will Gilmore needs very little vitamin Fe to prevent...

Iron Deficiency Anemia

Common in old fartz ...

Will, you are cured!!!
Jim...
 
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Feb 14, 2014
5,560
Hunter 430 Waveland, MS
If you want to remove the Fe from your well water, using Thinwater's charts...

Raise the pH to about 8 [ use baking soda] and let sit for a bit to see the FeOH settle out.
Filter it and then add back some lemon juice for taste and back to neutral.

No more Fe in you water.

Chemistry in action.
Jim...

PS: OMG don't do that, we add CO2 to the air!!:laugh:
PSS: Guess you have that Fe tinge to your well water... dang it
 

dLj

.
Mar 23, 2017
1,758
Belliure 41 Snug Harbor, Lake Champlain
With such small amounts of FE in the water is is a wonder our tastebuds allow us to taste the iron when we drink the water.
That's soluble iron. My water also has suspended iron in it. I'd have to dig out my water analysis, but it's got lots of iron in it...

dj
 
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Mar 26, 2011
2,909
Corsair F-24 MK I Deale, MD
That's soluble iron. My water also has suspended iron in it. I'd have to dig out my water analysis, but it's got lots of iron in it...

dj
FWIW, suspended iron is not going to contribute to conductivity.

In fact, precipiatating these metals to such low levels is not as easy as just changing the pH. The crystals that form are far too small to settle. But now we are wondering off-topic towards water treatment.
 
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dLj

.
Mar 23, 2017
1,758
Belliure 41 Snug Harbor, Lake Champlain
FWIW, suspended iron is not going to contribute to conductivity.

In fact, precipiatating these metals to such low levels is not as easy as just changing the pH. The crystals that form are far too small to settle. But now we are wondering off-topic towards water treatment.
Yeah, I have a small factory in my basement..

dj
 
Oct 19, 2017
6,850
O'Day 19 Littleton, NH
I have this in my well:
"Iron-oxidizing bacteria are chemotrophic bacteria that derive the energy they need to live and multiply by oxidizing dissolved ferrous iron. They are known to grow and proliferate in waters containing iron concentrations as low as 0.1 mg/L. However, at least 0.3 ppm of dissolved oxygen is needed to carry out oxidation."

I'm not concerned because my water is the best tasting water I know. No iron flavor.
The Iron-oxidizing Bacteria may actually be relevant to a thread on marine corrosion since they encourage oxidation of ferrous material. May not be a problem in saltwater, but there are plenty of freshwater areas with this bacteria around here.

-Will (Dragonfly)
 
Mar 26, 2011
2,909
Corsair F-24 MK I Deale, MD
I have this in my well:
"Iron-oxidizing bacteria are chemotrophic bacteria that derive the energy they need to live and multiply by oxidizing dissolved ferrous iron. They are known to grow and proliferate in waters containing iron concentrations as low as 0.1 mg/L. However, at least 0.3 ppm of dissolved oxygen is needed to carry out oxidation."...The Iron-oxidizing Bacteria may actually be relevant to a thread on marine corrosion since they encourage oxidation of ferrous material. ...

-Will (Dragonfly)
In fact, this is a very significant concern in iron diesel fuel tanks, although those are scarce in boats. I'm guessing it is relevant to wooden boats.
Wiki re. Microbial Influenced Corrosion
Does it apply to aluminum tanks? The iron oxidation does not and I am not aware of an analogous reaction with aluminum, but fuel bugs do create acidity which can cause severe pitting of aluminum diesel tanks. Aluminum is NOT recomended by anyone, including the USCG, because numerous failures with ethanol gas have been noted within just a few years.
 
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dLj

.
Mar 23, 2017
1,758
Belliure 41 Snug Harbor, Lake Champlain
In fact, this is a very significant concern in iron diesel fuel tanks, although those are scarce in boats. I'm guessing it is relevant to wooden boats.
Wiki re. Microbial Influenced Corrosion
Does it apply to aluminum tanks? The iron oxidation does not and I am not aware of an analogous reaction with aluminum, but fuel bugs do create acidity which can cause severe pitting of aluminum diesel tanks. Aluminum is NOT recomended by anyone, including the USCG, because numerous failures with ethanol gas have been noted within just a few years.
MIC would be very bad in an aluminum tank. You'd particularly have problems with the sulfate reducing bacteria. They can get the sulphur from the fuel. Although modern fuels are quite low in sulphur, there is likely enough to have a problem if you were to use an aluminum tank.

dj
 
Oct 19, 2017
6,850
O'Day 19 Littleton, NH
I read a little bit last night and it seems like there are some definitions that would be worth compiling for this endeavor. I had thought each election shell was called a valence, but Collier says only the outer shell is a valence. That is where covalent bonding happens.
The charge imbalance of an atom or molecule leads to bonding, the joining together of atoms to share outer electrons, or corrosion, the loss of electrons from one negatively charged atom or molecule to a positively charged atom or molecule.

-Will (Dragonfly)
 
Feb 14, 2014
5,560
Hunter 430 Waveland, MS
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