According to experts based on years of experience in the application of resin, and the process of stainless steel pickling production line and anti-corrosion engineering research, for different applications of the media conditions selected for anti-corrosion materials are summarized, hoping to provide reference to the stainless steel pickling production line anti-corrosion.
I. Preface
As stainless steel has superior corrosion resistance, wear resistance, toughness and good processing properties, is widely used in the aerospace, marine, military, chemical, energy and daily furniture, construction and decoration, transportation and other fields, market prospects, and the stainless steel pickling process is an essential part of stainless steel production and product processing. Stainless steel pickling process selected pickling solution is generally a mixture of a variety of acids, mainly sulfuric acid, nitric acid and hydrofluoric acid, etc. These mixed acids are very corrosive and have a strong oxidizing properties, the temperature of the corrosive medium is also relatively high, these corrosion-resistant materials put forward very high requirements for corrosion resistance.
Stainless steel pickling principle is the use of acidic liquid, remove the oxide surface of the steel surface after pretreatment epidermis, remove the surface of the metal ions, so that it has a wonderful finish. Pickling material form with washing, tube washing, plate washing, line washing, etc., regardless of what process of pickling, stainless steel pickling production line process from production to waste water waste gas recovery system between the various links are very strong corrosion state. Therefore, the choice of anti-corrosion materials is directly related to the normal use of equipment, workshop flooring, guttering, wastewater and waste gas recycling systems. The common pickling process is as follows.
(a) Acid washing section process flow
→ original acid storage → pre-cleaning section (about 3.5m) → sulphuric acid pickling section (about 12m) → HF + HNO3 mixed acid pickling section (about 14m) → cleaning section (three sections about 8m) → drying section (about 4m) → waste acid liquid recovery → waste water and waste gas treatment system
According to the above process of pickling process, the main places that need anti-corrosion treatment work are
1. acid (cleaning) washing of steel tanks and platforms.
2、Acid circuit system (including storage tanks and pipes for new acid system, acid circulation system and waste acid system).
3, Acid mist collection system (including tank cover and collection piping).
4. reinforced concrete flooring (including equipment foundation flooring), guttering and pits for the workshop.
(B) stainless steel pickling process of corrosive media
Stainless steel pickling process, each section has a different corrosive media, provided by a steel company’s pickling liquid media conditions are as follows.
1, the original acid liquid
Sulphuric acid: liquid concentration in the tank 150-300g/L, the temperature is <90 ℃, the original liquid concentration of 98%.
Nitric acid: concentration of 100-200g/L in the tank, temperature <90°C, original concentration 65%.
Hydrofluoric acid: the concentration of liquid in the tank is 40-60g/L, the temperature is <65℃, and the concentration of original liquid is 70%.
2、Mixed acid
Nitric acid and hydrofluoric acid: liquid concentration in the tank 40-60g/L, temperature <65℃.
3、Wastewater
Acidic wastewater containing various heavy metal ions, salts and fluoride ions.
4、Exhaust gas
Exhaust gas containing HF, NO×.
From the above medium conditions, it can be seen that the medium is very corrosive, especially the concentration and temperature of sulphuric acid and nitric acid are relatively high and have strong oxidizing properties. Experts from the China Epoxy Resin Industry Association emphasise that the storage of the medium and the equipment using the medium in the pickling process therefore have high requirements for anti-corrosion materials.
