Hi.

Too many years ago, a knowledgeable chemist engineer told me that an iron object would hardly rust ever again if treated with caustic soda.

 

What is the treatment? dipping in a solution? media blasting? burying the metal in it? what concentration, or else ?

 

Miguel

Whatever the reason, I have some practical support for the effect, from using caustic as an electrolyte in battery cells. The iron (big nails) never rusts while immersed, and when taken out after use and left lying around, only that part of the nail that was not immersed (for connection purposes) rusted.

 

As a side note, with iron as one electrode, both gassed, the bubbles from iron being large, probably oxygen. Perhaps there is a clue there, and perhaps carbon content plays a part.

 

(Electrolysis with no external power supply?.....neat.)

provides a physical barrier, the caustic forms an iron compound a few moleculse thick on the surface. the oxygen can't get to it but the voltage required to overcome this is non existant.

 

if you scratch it it will still rust.