I'm now doing a science project about rust converting.

I use tannic acid and phosphoric acid to react with rust to form a complex, which in turn protects the iron.

 

when i did the exp, a blue-black coating was formed, which should be the iron-tannate complex, but the coating was somehow detached no matter how long i react the acids with rust. What can I do to improve the process?

Frankly speaking I’m not quite familiar with rust converting. But I think the reason of this failure is that the acids can’t penetrate very well. Maybe you can add some organic solvent to bring the acids into the rust…

 

Keep going!

Immersing a rusty iron piece in baking soda solution and applying 12 volts electrolytically removes the iron oxide.

 

Many years ago, an expert told me that immersing a rusty piece in caustic soda, would prevent from rusting ever again

I've heard that too... not sure on the details.

Maybe you should know what the blue-black coating is before making any conclusion.. You can try using the XRD to analyze the composition. Maybe the composition of the coating is somehow still active or chemically unstable before forming a protective passive layer.

My english is sadly poor but I'm proud to be Malaysian :')

Immersing a rusty iron piece in baking soda solution and applying 12 volts electrolytically removes the iron oxide.

 

Many years ago, an expert told me that immersing a rusty piece in caustic soda, would prevent from rusting ever again

 

http://en.wikipedia.org/wiki/Passivation

 

what happens is that you form a thin layer(pretty much just a few molecules deep) on the surface of the metal that prevents oxygen getting to the metal and corroding it.

Immersing a rusty iron piece in baking soda solution and applying 12 volts electrolytically removes the iron oxide.

 

Many years ago, an expert told me that immersing a rusty piece in caustic soda, would prevent from rusting ever again

 

I don't really sure but i would say that the primary corrosion product of iron is Iron hydrous oxide (Fe(OH)3) not iron oxide. Iron oxide is more tend to form iron hydroxide (red-brown rust) when exposed to humidity.

 

 

the expert may be right.. but rusting will only stop as long as the piece is immersed in the solution

http://en.wikipedia.org/wiki/Standard_electrode_potential

Edited February 28, 201015 yr by Newbies_Kid
Consecutive posts merged.