Bit of a strange question. Mostly theoretical.

Imagine I have some salty water and I stick some steel wool (or similar) in it so that it starts to rust. Now, the salty water contains dissolved oxygen too. In the rust reaction that starts going on – will the iron react with the dissolved oxygen in the water, or will it take oxygen from splitting the water molecules?

Or to put it another way, will adding some rustable iron to salty water lower the dissolved oxygen?

What if I added to an electric current to speed up the rusting process?

party_pants said:

Bit of a strange question. Mostly theoretical.

Imagine I have some salty water and I stick some steel wool (or similar) in it so that it starts to rust. Now, the salty water contains dissolved oxygen too. In the rust reaction that starts going on – will the iron react with the dissolved oxygen in the water, or will it take oxygen from splitting the water molecules?

Or to put it another way, will adding some rustable iron to salty water lower the dissolved oxygen?

What if I added to an electric current to speed up the rusting process?

You need my Dad for that. Electrolysis engineer. He did the cathodic protection on the Bass Strait gas rigs. But that was a long time ago (1960s) and he can’t talk now. So we will have to wait for someone here.

Are you thinking along the lines of liberating hydrogen from the rust process?

Peak Warming Man said:

Are you thinking along the lines of liberating hydrogen from the rust process?

No. I am thinking about removing dissolved oxygen.

party_pants said:

Peak Warming Man said:

Are you thinking along the lines of liberating hydrogen from the rust process?

No. I am thinking about removing dissolved oxygen.

Boil the water

wookiemeister said:

party_pants said:

Peak Warming Man said:

Are you thinking along the lines of liberating hydrogen from the rust process?

No. I am thinking about removing dissolved oxygen.

Boil the water

a few times.

monkey skipper said:

wookiemeister said:

party_pants said:

No. I am thinking about removing dissolved oxygen.

Boil the water

a few times.

Or put it in a vacuum chamber I bet

wookiemeister said:

party_pants said:

Peak Warming Man said:

Are you thinking along the lines of liberating hydrogen from the rust process?

No. I am thinking about removing dissolved oxygen.

Boil the water

I still want the dissolved nitrogen, carbon dioxide and others, just want to remove the oxygen.

Another job for drones

Shark Spotting

https://www.abc.net.au/news/2019-06-09/drone-data-from-popular-nsw-beaches-reveals-shark-hotspots/11189244

Tau.Neutrino said:

Another job for drones

Shark Spotting

https://www.abc.net.au/news/2019-06-09/drone-data-from-popular-nsw-beaches-reveals-shark-hotspots/11189244

People seem shocked that there are sharks in the ocean, going about their own daily sharky business.

all of the

party_pants said:

Bit of a strange question. Mostly theoretical.

Imagine I have some salty water and I stick some steel wool (or similar) in it so that it starts to rust. Now, the salty water contains dissolved oxygen too. In the rust reaction that starts going on – will the iron react with the dissolved oxygen in the water, or will it take oxygen from splitting the water molecules?

Or to put it another way, will adding some rustable iron to salty water lower the dissolved oxygen?

What if I added to an electric current to speed up the rusting process?

> will the iron react with the dissolved oxygen. will adding some rustable iron to salty water lower the dissolved oxygen?

Yes, with the dissolved oxygen and yes, it will lower the dissolved oxygen (if it occurs fast enough). The water doesn’t have to be very salty.

Steel wool soap pads rust fast, but not sure if the soap would interfere with the experiment. As an alternative to steel wool, perhaps iron filings?

Dissolved oxygen diffuses towards the rustable iron. But on the other hand it also diffuses downwards from the surface. In still water, the diffusion rate is laminar diffusion. In stirred water, the diffusion becomes much faster. BUT don’t stir it so fast that the water surface breaks up, keep the stirring as as horizontal as possible.

Adding rustable iron to water will lower the dissolved oxygen, but it’s difficult to say by how much because the final value will be a balance between the two diffusion rates.

I once tried to calculate the rate of rusting of steel chain in a lake, and found it impossible to calculate. There simply wasn’t enough information out there to calculate it. I called in an expert on corrosion and he couldn’t calculate it either. (It’s sort of as difficult to calculate as the rate of fire spread, ie. it’s much easier to set up a test and measure it than to do the calculation).

> What if I added to an electric current to speed up the rusting process?

Um, I ought to know the answer to this one, but …

In the absence of an electric current, it’s the differences in grain orientation and composition across grain boundaries that allows electrons to migrate from one to the other.

Too high a voltage and the water will break down, but what voltage is that? Check web, if the voltage below 1.2 volts then there is no breakdown of water.

My hunch is that a voltage of 1.1 volts is applied to opposite ends of steel wool would greatly speed up the corrosion rate. But I’m not sure of that. An experiment perhaps.

You could unethically put a gold fish in the water and see if it suffers ill effects, filter the rust and other muck out so they don’t mess up the experiment.

• You could unethically put a gold fish in the water and see if it suffers ill effects, filter the rust and other muck out so they don’t mess up the experiment.

You would need a salt water fish. But you could also get a dissolved oxygen tester…

Cymek said:

You could unethically put a gold fish in the water and see if it suffers ill effects, filter the rust and other muck out so they don’t mess up the experiment.

Not goldfish. Goldfish can breathe by gulping in air from above the water surface. So can a lot of other freshwater fish.

High salt concentration is not an essential for the experiment.

Thinking further. In still water, oxygen diffuses down from the surface until the net downwards diffusion matches the uptake of oxygen from the rusting. But it can also work the other way. In still water, oxygen diffuses upwards to be released into the atmosphere.

Would putting fish into still water have the same effect as rusting iron, as the respiration from the fish also removes oxygen from the water.

What’s the purpose of removing only dissolved oxygen ?

wookiemeister said:

What’s the purpose of removing only dissolved oxygen ?

Growing algae in the water.