[uperkurk]

Hey, what chemical is the most corrosive to iron and steel? what chemical can corrode rock, ie, make it very weak and unstable?

[uperkurk]

Wow this forum is popular, over 90 views and not one reply lol

[Borek]

Question is so vague that it can't be reasonably answered.

[uperkurk]

Ok let me elaborate, if i had a rock about the size of a football and i poured some sulphuric acid on it would it start eating away at the rock?

and about the metal is sulphuric acid effective at corroding the steel/iron or would it take weeks for it to corrode? 

[Borek]

Ok let me elaborate, if i had a rock about the size of a football and i poured some sulphuric acid on it would it start eating away at the rock?

Depends on the kind of the rock.

and about the metal is sulphuric acid effective at corroding the steel/iron or would it take weeks for it to corrode? 

Depends on the kind of the steel.

[uperkurk]

The rock would be igneous and sedimentary and with the steel im saying it would be tough reinforced steel. I dont really know much bout the steel I think it would be easier to say, what types of steel/iron CANT sulphuric acid corrode? When i say rock I mean the good old concrete stuff that they use for supporting of buildings and building blocks for buildings

[Borek]

In sulphuric acid acid resistant steel will survive, other steels will get corroded. But then most types of steel will not corrode in concentrated nitric acid due to passivation.

As for the stone - limestone will get easily dissolved in sulphuric acid, while most silicate minerals will be more or less resistant.

[uperkurk]

Thanks, are there any chemicals that when combined become an effective corrosive for reinforced steel?

The reason I ask is that ive been told that if you had a steel bar 1.5" thick and put it in sulphuric acid and left it for a while the bar would become extremely weak and could be broken by hand. Is this false or would it just have a rust effect on the bar and still be very strong?

[Borek]

There is a grain of truth in what you have beed told. Assuming very specific situation - 1.5" rod, that have to be eaten uniformly to left just a few milimeters rod that can be bent by hand, you need around a pound of concentrated acid per inch of the rod. This is simple stoichiometry.

In fact you don't need acid for that, it is enough that steel rods are too close to the surface of concrete and they can be reached by water that always slightly penetrates concrete. In the presence of water iron will corrode producing oxides that have higher volume than original rod. That means pressure, and pressure will burst the concrete (albeit slowly) making cracks through which more water and oxygen can reach the iron. Process speeds up then, and corrosion proceeds along the rod into the voulme.

[uperkurk]

Thanks for taking the time to reply. You have answered my questions in detail, many thanks.