What protects the stomach wall from the potential damage by this chemical products?

Answer 1

The mucous is the substance that protects the stomach walls from digestion. The mucous cells are found throughout the stomach lining and secrete mucus which protects the stomach from its own digestive secretions.

Answer 2

I think that when you have food in your stomach, the acid would rather eat the food than the walls of your stomach.
That is one way you get stomach pains: no food in your stomach, so the acid "bites" your stomach wall.

Answer 3

The stomach wall is protected by a layer of mucus that acts as a physical barrier and helps to prevent damage from acidic digestive juices. Additionally, the stomach lining contains specialized cells called goblet cells that secrete bicarbonate ions, which help neutralize stomach acid. Mucosal blood flow also helps to repair any damage that may occur.