The corrosion of glass fibres in acid solution is well known and is thought to be responsible for many instances of failure in glass reinforced plastic materials. However, the chemical mechanism and rates of corrosion are still not fully understood. For example, it is not simply the acidic strength of the corroding medium that affects the rate but in many cases the anion associated with the acid plays a major role. Aqueous oxalic acid, a relatively weak organic acid, is particularly severe and causes almost total loss of strength in glass fibres after exposure for only a few days. On the other hand, nitric acid, which is a much stronger mineral acid, takes about 3 weeks to cause the same strength loss. Perchloric acid, an even stronger acid, is much less effective and, at a concentration of 5 molar, causes only 10% strength loss in about 4 weeks.
