Cactus a rust remover? What?

E

Endololz

Joined
Apr 10, 2012
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177
Well a while ago I was playing with one of my SOG knives that had a bead blasted blade with more rust spots on it than I would mind having and I decided to chop up a cactus. When I was done hacking the cactus apart and I wiped my blade down I notice the rust was gone. My thought was that I could not see the rust because of the angle of the knife but when I inspected the blade there was no rust anywhere. Today I saw some stains/rust on my Delica and I went at chopped up the cactus again to see if it would work and there is no more rust on it. So I am wondering if anyone else has noticed that cactus removers or covers up rust, and if you have a blade that has a little rust on it and are willing to chap a cactus up see if it removes the rust.
 
Perhaps it has acidic juice.
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easy enough to test grind some up and put into an aqueous solution with distilled water and test with pH paper or litmus. You can make homemade indicator by boiling red cabbage in a concentrated amount of water than get your test with a base (NaOH and acid HCl or similar) then test to see if it is acid base or neutral. I would think more likely the cactus has fine particles that work like a fine simichrome polish and physically remove the rust. I've never tried to remove FeO with HCl but I guess it would theoretically work FeO + 2 HCl -> FeCl2 + H2O
 
It might also have been the abrasive skin that removed light surface discoloration.
 
Well I think tomorrow I am going to get some of the cactus I used and buy some cheap high carbon steel and let it rust a little and do some tests on the blades and see what the cactus does to the steel and rust. I will try to post updates on what I am doing to the blades in this thread to any of you who are interested in the topic.
 
TNP Dude said:
easy enough to test grind some up and put into an aqueous solution with distilled water and test with pH paper or litmus. You can make homemade indicator by boiling red cabbage in a concentrated amount of water than get your test with a base (NaOH and acid HCl or similar) then test to see if it is acid base or neutral. I would think more likely the cactus has fine particles that work like a fine simichrome polish and physically remove the rust. I've never tried to remove FeO with HCl but I guess it would theoretically work FeO + 2 HCl -> FeCl2 + H2O
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Yeah...

:rolleyes:

Now that you've asserted your "intellectual dominance" over the rest of us non-chemists, can we get a layman's terms version? ;)

You'll probably fit right in here, by the way. :)
 
TNP Dude said:
easy enough to test grind some up and put into an aqueous solution with distilled water and test with pH paper or litmus. You can make homemade indicator by boiling red cabbage in a concentrated amount of water than get your test with a base (NaOH and acid HCl or similar) then test to see if it is acid base or neutral. I would think more likely the cactus has fine particles that work like a fine simichrome polish and physically remove the rust. I've never tried to remove FeO with HCl but I guess it would theoretically work FeO + 2 HCl -> FeCl2 + H2O
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Side reactions often occur with acid resulting in rust. Think of what happens when your car gets hit by acid rain...turns into a rust bucket :P
 
Many cactus' have cells present called sclereids. Sclereids are lignified (contains lignin, a substance similar to fibre) cells which are often very tough and gritty. Pears have tons of sclereids as well, which gives them that characteristic gritty texture.

My theory is that the cactus you cut up had these sclereids which acted as an abrasive. Some cacti can be acidic as well, so it may have been a combination of lower pH and grit. You might have stumbled upon an organic sand-paper. Cool.
 
Many cactus' have cells present called sclereids. Sclereids are lignified (contains lignin, a substance similar to fibre) cells which are often very tough and gritty. Pears have tons of sclereids as well, which gives them that characteristic gritty texture.
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I thought it would be something like this. It really makes a lot of sense, the abrasives cactus are there but unlike paper they are suspended in the fruit (fruit?) like a good polish and can work on the rust more effectively. I really think that the best way to remove rust is a physical process (sanding, grinding, polishing) rather than a chemical one.


Now that you've asserted your "intellectual dominance" over the rest of us non-chemists, can we get a layman's terms version?
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:D lol It is sort of fun to apply my chemistry knowledge to a knife problem.

basically if you take the cactus and grind it up in a mortar and pestle then put it in water to make a solution (this is so you can test the pH easier) you can test with strips or a special chemical called litmus (or any indicator). An indicator indicates wether a substance is a acid, base, or neutral.

Now in my example I was using HCl or hydrochloric acid. This is a strong inorganic acid and therefore has a high disassociation rate. The juice in the cactus would be an weak acid like orange juice ( this is why when you drink orange juice it does not melt your teeth). This is something that I forgot about.


Side reactions often occur with acid resulting in rust. Think of what happens when your car gets hit by acid rain...turns into a rust bucket :P
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Right. In the example I gave the products were FeCl[SUB]2[/SUB] and H[SUB]2[/SUB]O. Now this would be the reaction just with the rust and would give you a salt and water. Without doing a test I think that the salt would be in an liquid state ( technically called aqueous) so therefore it could be removed. But yes the side reactions. Many metals when submerged into HCl dissolve and give off hydrogen gas (example: Mg (s) + HCl (aq) --> MgCl[SUB]2[/SUB] (aq) + H[SUB]2[/SUB] (g) ) So if you used hydrochloric acid to remove rust you would most likely dissolve your whole knife blade into the solution of acid :p So yes there are side reactions as well and I am sure I have forgotten (and am too lazy) about many reactions that would also take place here.


I'm watching this thread to see if the cactus juice really removes rust.
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I really think that it is more the physical structure of the cactus than the juice but it will be interesting to find out
 
timbit said:
Many cactus' have cells present called sclereids. Sclereids are lignified (contains lignin, a substance similar to fibre) cells which are often very tough and gritty. Pears have tons of sclereids as well, which gives them that characteristic gritty texture.

My theory is that the cactus you cut up had these sclereids which acted as an abrasive. Some cacti can be acidic as well, so it may have been a combination of lower pH and grit. You might have stumbled upon an organic sand-paper. Cool.
Click to expand...

If memory serves correctly those are often referred to as "stone cells" and are thought to appear in pears to act as a bowel irritant in birds, causing them to deposit the pear's seeds before their digestive system can break them down.
 
Some plants such as 'Horsetails' (Equisetum), have a high silica content to the point that you can scour a pot with them. I would not be at all surprised if this is the mechanism in your cactus.
 
This is very interesting, and is a easy way to clean a blade, although I think I will just use flitz for now.
 
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