# Why are acids corrosive?

I'm in the second year of my biochem major, taking organic chemistry, and I feel like I've learned a lot about acids. The most popularly recognizable property of acids is their corrosive power. There are pop-culture depictions of acids everywhere, and all they seem to do is corrode stuff. Yet, with all I've learned about them, it's never been explained to me why they have this property, or how and when it works.

• Not all acids are considered corrosive. The strong acids which are corrosive are highly reactive so they react with most material they come into contact with and the by products start to dissolve in the acid corroding the material. – Technetium Dec 7 '15 at 1:59
• The reactivity of the anion towards the exposed material also plays a role in the acids potential to corrode. – Technetium Dec 7 '15 at 10:41

Strong acids disassociate completely, weak acids do less so. When they do disassociate in water, they form $\ce{H3O+}$. This pulls the electrons from the thing it is reacting with. Lets take this to be Fe. ($\ce{H3O+}$ rips the electrons from the substance). So the reaction would go something like: $\ce{Fe + 2H3O+ -> Fe^2+ + 2H2O + H2}$. The $\ce{Fe^2+}$ formed is soluble in water. This also reacts with the other ion from the acid. This is what makes the acids corrosive.

• So you're saying that acids have a tendency to take electrons from things, and things with fewer electrons tend to be more soluble? Like I know that metals seem to tend to do that, but is that sort of a general trend? Like maybe taking electrons like that tends to polarize things and the now-polar things tend to be more soluble? – Raiden Worley Dec 8 '15 at 10:05
• Things don't neccassarily have to be soluble for the reaction. Even submersion in an acidic solution will work. I will talk mostly about H+ (as this is the only true acid according to bronsted-lowry theory (ignoring the proton acceptors as acids (lewis theory) as they function in the same way but a little less strongly)). This is a single proton. It is highly positive and this charge is what makes it so electronegative. Meaning that it has a very high tendancy to gain (simply rip off (force) from anything) electrons off of other things which makes them "vulnarable" for reaction with other ions – Sarthak Garg Dec 9 '15 at 5:13