What is this indelible mess on the glass?

Today, glass has become one of the most important materials in daily life, production and science and technology. In everyone's cognition, it may be felt that the glass in life is a very stable substance, which is not easy to corrosion. However, if you carefully observe the bedroom mirror or the glass on the window, you will find that with the extension of the use of time, the glass surface will appear white fog, white spots, even after wiping with water can not be removed.

These white fog, white spots are not dust, but the product of glass corrosion, and some people use "glass weathering" and "glass mold" to describe this corrosion phenomenon. At the turn of spring and summer, the temperature and humidity gradually rise, which will greatly increase the probability of glass corrosion. For the building window glass that simply withstands the erosion of atmospheric substances, its corrosion can be divided into four stages:

1. Substances such as water, carbon dioxide and dust in the air will be adsorbed on the surface of the glass to form deposits, but this surface deposit is easy to clean with water.

2. If the glass has been in high humidity conditions (more than 60%), the sediment on the surface will become thicker (about 1μm), water or moisture will spread to the glass, and the surface will change color after hydrolysis of the glass components, which can still be cleaned with water.

3. After the deposition film is formed on the surface of the glass, if it continues to be in a high humidity atmospheric environment, some components (alkali metals and alkaline earth metals) will be enriched and leached on the surface of the glass, and the soluble silicate on the surface will be destroyed.

At this time, there will be a high silicon content in the local location, which looks like the residue of water stains, the slightly corroded part can be cleaned with vinegar, and the serious corrosion can even be effectively cleaned with the hydrofluoric acid mentioned earlier. 4. In the final stage, the glass surface will become very rough, and serious corrosion will occur locally. This is because the sodium ions in the glass move out of the matrix and react with the air to produce white alkaline substances, which is the white fog and white spots on the glass, even the use of hydrofluoric acid can not achieve effective cleaning.

Take an example in life: the longer the mirror is used, it will feel more and more blurred, which is because the surface has been corroded, become more rough, and the incident light part of the diffuse reflection. From the first stage of glass corrosion to consider, gently wipe with water every week to keep the mirror clear and clean, its service life can be extended.

In addition to white fog, white spots, glass corrosion will also appear rainbow spots, its cause is more complex, can be divided into two types:

1. Produced during the production process, also known as stress spots. At present, there is no way to avoid interference of incident light due to uneven stress distribution in glass. 2. Produced during use, it is eroded by water vapor in the air or other chemical products.

Although glass corrosion will bring trouble to our lives, it is a useful processing means in the glass processing process. In addition to direct engraving, etching agents (HF, hydrofluoric acid) can also be used to etch the glass. The glass is coated with paraffin liquid dissolved in gasoline as a protective layer, and the required text or pattern is carved on the solidified paraffin layer, and the depth of the scratch should be able to expose the glass; Then, the hydrofluoric acid is dropped on the text or pattern, the corrosion time is controlled, the depth of the required pattern is adjusted, and the paraffin and hydrofluoric acid are washed with warm water, and the glass with the pattern can be made. (Not recommended to operate yourself, hydrofluoric acid is strongly corrosive)