一.The introduction of ferric chloride etching solution:
Ferric chloride chemical formula: FeCl3=FeCl3·6H2O, ferric chloride is a covalent compound, and is currently the most cost-effective and most widely used chemical for stainless steel SUS304 corrosion in the etching (corrosion) industry. Ferric chloride is easily soluble. It is watery and has strong water absorption. It absorbs water from the air and deliquesces. Some solid ferric chloride will automatically absorb water and convert into hydrate in the air with high humidity. This process is called deliquescence. After deliquescent, the crystal water of ferric chloride has been destroyed, and the original mineral lattice is destroyed. When destroyed, other atoms can be recombined to form another compound that forms ions and molecules other than the crystalline water FeCl3·6H2O. Therefore, when purchasing ferric chloride, try to choose solid ferric chloride with the shortest weathering time and the shortest production date.
For the chemical corrosion of stainless steel SUS304, ferric chloride has the lowest volatilization rate relative to other chemicals, the lowest production cost, the smallest environmental pollution, and the strong circulation due to the widespread use of sewage treatment plants. Stainless steel in the long-term corrosion process will destroy the mineral lattice of ferric chloride itself. In order to prolong the use time of ferric chloride, many people will add some small amounts of strong acids, such as hydrofluoric acid, hydrochloric acid, sulfuric acid, nitric acid, etc. Or an oxidized product that reacts with ferric chloride itself to reduce the destroyed crystal water and enhance the etching factor, thereby improving the corrosivity of the ferric chloride to the stainless steel, in fact, no matter what kind of chemicals are used, as long as it can be restored 6 water (crystalline water) is the best state
二. the new drug water reaction process
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 + sheet etching finished product + water + stainless steel impurities
三. Reasons for the reduction of medicinal properties and methods of reduction
As the chemical reaction progresses, the etchant liquid is lowered because the ferric chloride is oxidized to ferrous chloride. At this time, it is necessary to reduce the ferrous chloride to ferric chloride to increase the acidity of the solution. It is necessary to add an aqueous solution of reducing agent), hydrochloric acid (inhibitor) to produce ferrous hydroxide due to the easy hydrolysis of ferrous ions in water: FeCl2+H2O=, Fe(OH)2+HCL, in order to prevent hydrolysis and deterioration of ferrous chloride, Some hydrochloric acid is often added to the ferrous chloride solution; since hydrochloric acid is easily volatilized, the following reaction occurs as the chemical reaction proceeds: 6FeCl2+NaClo+3H2O=4FeCl3+2Fe(OH)3 ↓+NaCl ferrous chloride + sodium chlorate + water = ferric chloride + iron hydroxide (precipitate) + sodium chloride (where iron hydroxide is a precipitate, so as the chemical reaction time is lengthened, viscous substances will appear in the medicine box To remove the viscous precipitate, physical filtration is required, such as filter filtration or water purification.
