Etching process: Reaction equation of chemical etching by etching machine

Mainly focused on corrosion processing of stainless steel US304

Etching machine Add chemical etching solution: ferric chloride

chemical formula: FeCl3=FeCl3·6H2O

One Optimal conditions for etching solution

baume degrees: 38°—42°

Liquid temperature: 45°—50°

PH value measurement range: 1PH-3PH

Oxidizer FeCl3

II The reaction process of the new medicine

The etching of stainless steel by ferric chloride etching solution is an "oxidation-reduction" process:

1. Oxidation reaction: 2FeCl3 Fe=3FeCl2

Ferric chloride stainless steel water=ferrous chloride plate etched finished water stainless steel impurities

III Reasons and reduction methods for the decrease in medicinal properties of potions

As the chemical reaction progresses, the chemical properties of the etching solution decrease because ferric chloride is oxidized to ferrous chloride, which needs to be reduced to ferric chloride to increase the acidity of the solution. Sodium chlorate aqueous solution (reducing agent) and hydrochloric acid (inhibitor) need to be added

2. Reduction reaction: 2FeCl2 NaClO 2HCL=2FeCl3 NaCl H2O

Ferrous chloride sodium chlorate hydrochloric acid=ferric chloride sodium chloride water (Due to the easy hydrolysis of ferrous ions in water, ferrous hydroxide is produced: FeCl2 H2O=, Fe (OH) 2 HCl. Therefore, in order to prevent the hydrolysis and deterioration of ferrous chloride, some hydrochloric acid is often added to the ferrous chloride solution.)

3. Due to the volatility of hydrochloric acid, the following reactions may occur as the chemical reaction progresses:

6FeCl2 NaClo 3H2O=4FeCl3 2Fe(OH)3 ↓ NaCl

Ferrous chloride sodium chlorate water=ferric chloride ferric hydroxide (precipitate) sodium chloride

(Among them, iron hydroxide is a precipitate, so as the chemical reaction time increases, viscous substances will appear in the medicine box. To remove this viscous precipitate, physical filtration methods such as filter screens or water purification devices need to be used.)

Definition and Understanding

Ferric chloride is a covalent compound and currently the most cost-effective and widely used chemical in the etching (corrosion) industry for the corrosion of stainless steel US304. Ferric chloride is easily soluble in water and has strong water absorption properties, which can absorb water from the air and deliquescence. FeCl3 melts with 6 crystal waters FeCl3 · 6H2O, also known as bound water. Crystalline water is water molecules bound to compounds, and they are not liquid water. Many crystals contain crystal water, but not all crystals contain crystal water. When a solute crystallizes and precipitates from a solution, a certain number of water molecules are bound to the crystal, and these water molecules are called crystalline water. In crystalline substances, a certain number of water molecules that are bound to ions or molecules by chemical bonding forces, such as those affected by external factors. For example, under gradually increasing temperature conditions, CuSO4 · 5H2O can gradually lose its crystalline water and transform into CuSO4 · 3H2O CuSO4·H2O 、CuSO4。 Some hydrates may undergo hydrolysis reactions with the crystal water they contain when heated, transforming into oxides or basic salts. When a hydrate is exposed to relatively dry air, it slowly loses its crystal water and transforms from hydrate crystals into a powdery anhydrous substance. This process is simply understood as weathering, which means that when purchasing solid ferric chloride, a portion of the crystal water has already been lost. Therefore, choosing a reputable manufacturer of ferric chloride is particularly important. Some solid ferric chloride will automatically absorb moisture and transform into hydrates in humid air, a process called deliquescence. After deliquescence, the crystal water of ferric chloride has been destroyed, and the original mineral lattice is destroyed. Other atoms can recombine to form another compound, which is the formation of ions and molecules other than FeCl3 · 6H2O, CuSO4 · 3H2O, CuSO4 · H2O, CuSO4. Therefore, when purchasing ferric chloride, it is advisable to choose the solid ferric chloride with the shortest weathering time and production date. Regarding the corrosion of stainless steel US304, ferric chloride has the lowest volatilization rate, production cost, and environmental pollution compared to other chemicals. Additionally, due to its widespread use in sewage treatment plants, it has strong fluidity. During the long-term corrosion process of stainless steel, the mineral lattice of ferric chloride itself will be destroyed. In order to prolong the use time of ferric chloride, many people will add a small amount of strong acid, such as hydrofluoric acid, hydrochloric acid, sulfuric acid, nitric acid, etc., or oxidizers that react with ferric chloride itself to reduce the damaged crystal water, thereby improving the corrosiveness of ferric chloride on stainless steel. In fact, no matter what chemicals are used, as long as they can be reduced to the optimal state of 6 water (crystal water), it is sufficient. However, in addition to the following parameters that our factory provides based on years of experience for the optimal value of ferric chloride corrosion solution for US304 stainless steel.