When we hear “chemically attack”, we think of reactions that occur fast enough for us to observe such as corrosion. Compounds that are strong oxidizers, such as halogens or some acids, behave in this way. Most chemical reactions involve oxidation and reduction, in which electrons are transferred from one species (that which is oxidized) to another (that which is reduced.) Two substances that have dissimilar tendencies to gain electrons are more likely to react in this way. Galvanic corrosion occurs when two dissimilar metals are in contact with each other and exposed to weather.
We are all familiar with iron rusting, a form of corrosion. When this happens iron is oxidized from neutral Fe to Fe3+ in the compound Fe2O3. At the same time, O2 is reduced to 02-. This occurs spontaneously because oxygen has a high tendency to gain electrons and iron has a high tendency to lose electrons.
The following are examples of some common substances that are known to be reactive or “attack” other substances chemically:
Acids such as HCl (acids tend to react with metals)
Bases such as NaOH (lye)