What is Hydrochloric Acid ?

Hydrochloric acid is the aqueous solution of hydrogen chloride (HCl), which is a strong inorganic acid of one element. Hydrochloric acid is a colorless and transparent liquid with a strong pungent smell and high corrosiveness. Concentrated hydrochloric acid (about 37% by mass) is highly volatile — it combines with water vapor in the air to form small droplets of hydrochloric acid that create an acid fog over the top of the bottle. Hydrochloric acid is the main component of stomach acid, it can promote food digestion, resist microbial infection.

Hydrochloric acid is the aqueous solution of hydrogen chloride (HCl) gas and one of the six inorganic strong hydrochloric acids ( H2SO4, HNO 3, HCl, HBr, HI, HClO 4)

What is PVC?

PVC, also known as polyvinyl chloride, is made of polyvinyl chloride, and other ingredients are added to improve its heat resistance, toughness, ductility, etc. . The top layer of the film paints, the main ingredient in the middle is polyvinyl chloride, and the bottom layer is back coating adhesive.

PVC surface coating has anti-corrosion, and polyvinyl chloride, and hydrochloric acid, caustic soda does not react.

More About Hydrochloric Acid

Applications

• In daily life, as Hydrochloric acid can react with insoluble CACO3 and MG (OH)2 to form soluble salts, so hydrochloric acid can be used to remove water rust and limescale in the pipeline.
• In industry, hydrochloric acid is an important basic chemical raw material and is widely used. Mainly used in the production of chloride, aniline, and dyes, and other products.
• In hydrometallurgy, it is used to extract a variety of rare metals.
• Hydrochloric acid is commonly used in organic synthesis, textile bleaching, and dyeing, petroleum processing, leather and papermaking, electroplating fusion welding, and metal pickling.

• Hydrochloric acid is essential in the production of organic drugs such as procaine, thiamine hydrochloride, and glucose.
• In the preparation of animal glue, a variety of dyes when hydrochloric acid is also useful.
• In the food industry, hydrochloric acid is used to make monosodium glutamate and chemical soy sauce.
• Doctors also direct patients with gastric acid deficiency to take extremely dilute hydrochloric acid to treat indigestion.

Potential Threat to Human Health

On October 27, 2017, the International Agency for research on cancer (IARC) of the World Health Organization (WHO-RRB- published a preliminary collation of the list of carcinogens. Although it is not listed as a carcinogen due to insufficient evidence, its harm to the human body can not be ignored.

Concentrated hydrochloric acid (fuming hydrochloric acid) evaporates an acid fog. Hydrochloric acid itself and acid fog can corrode human body tissue, may irreversibly damage respiratory organs, eyes, skin and gastrointestinal, and so on. When hydrochloric acid is mixed with an oxidant such as bleach, sodium hypochlorite, or potassium permanganate, the poisonous gas chlorine is produced.

The United States Environmental Protection Agency has classified hydrochloric acid as toxic.

The danger of hydrogen chloride depends on its concentration. The European Union classification of hydrochloric acid solutions is shown in the table below.

Classification of hydrochloric acid solutions (EU)

Safety Cautions

It is recommended to wear personal protective equipment when using hydrochloric acid to reduce the risk of handling hydrochloric acid, including latex gloves, goggles, corrosion-resistant clothing, and shoes.

Emergency Treatment

• Skin contact: Immediately remove contaminated clothing, rinse with plenty of running water for at least 15 minutes, can smear weakly alkaline substances (such as alkaline water, soap water, etc.) , see a doctor.
• Eye contact: Lift your eyelids immediately and rinse thoroughly with plenty of running water or saline for at least 15 minutes and go to the hospital.
• Inhalation: Move quickly to a place of ventilation. If your breathing is difficult, give oxygen immediately. If breathing stops, give mouth-to-mouth immediately and See a doctor.
• Food Intake: Gargle with plenty of water, swallow a large number of raw egg white or milk (no baking soda and other drugs) and then go to the hospital.

Summary

Generally speaking, PVC pipe itself has high corrosion resistance, it is recommended to use 5%-10% of low concentration of hydrochloric acid mixed corrosion inhibitor to clean the PVC pipe. (High concentration hydrochloric acid has a strong corrosion effect, it’s not suitable for use in cleaning).

In addition, for metal pipes, hydrochloric acid cleaning is not recommended, as dilute hydrochloric acid can dissolve many metals (react chemically with K, Ca, Na, Mg, Al, Zn, Fe, Sn, Pb) that are reactivity series to hydrogen, metal chloride, and hydrogen gas), so stainless steel pipes, galvanized pipes and iron pipes should never be cleaned with hydrochloric acid.

But there is the thing, the activity of copper, silver, and other metals after hydrogen can not react with dilute hydrochloric acid, but when the copper is in the presence of air, it can dissolve slowly. So for copper pipe, if hydrochloric acid must be used, cleaning should be very careful.

Ceramic pipes are also not recommended to be cleaned with hydrochloric acid, which dissolves calcium carbonate in the ceramics.