There are mechanical methods, chemical methods, and electrochemical methods to remove scale on sanitary stainless steel pipes.
Due to the complexity of the scale composition of sanitary stainless steel pipes, it is not easy to remove the oxide scale on the surface and make the surface high to a high degree of clarity and smoothness. Removing the scale of sanitary stainless steel pipes usually takes two steps, the first step is pretreatment, and the second step is ash removal.
The pretreatment of the scale of the sanitary stainless steel pipe makes the scale lose, and then pickling is easy to remove. Pretreatment can be divided into the following ways: Alkaline nitrate melting treatment method. The alkaline melt contains 87% hydroxide and 13% nitrate. The ratio of the two in the molten salt should be strictly controlled so that the molten salt has the strongest oxidizing power, the best melting point, and the smallest viscosity. In the manufacturing process, only study sodium nitrate-containing halo not less than 8% (wt). The treatment is carried out in a salt bath furnace, the temperature is 450~470 °C, and the time is 5 minutes for ferritic stainless steel and 30 minutes for austenitic stainless steel. Similarly, iron oxides and spinels can also be oxidized by nitrates to become lose trivalent iron oxides, which are easily removed during pickling. Due to the high-temperature effect, the oxides that appear are partially peeled off and sink into the bath in the form of sediment. furnace bottom.
Alkaline nitrate melting pretreatment process: steam degreasing → preheating (150~250°C, time 20~30min) → molten salt treatment → water quenching → hot water washing. Molten salt treatment is not suitable for assemblies with weld gaps or curling. When the parts are taken out of the molten salt furnace and quenched in water, a burst of irritating alkali and salt spray will be splashed. Splash-proof quenching tank. When water quenching, hang the parts basket into the tank first, stop above the water level, close the tank cover, and then lower the parts basket into the water until it is submerged.
Alkaline potassium permanganate pretreatment: the treatment solution contains sodium hydroxide 100→125g/L, sodium carbonate 100→125g/L, potassium permanganate 50g/L, solution temperature 95~105℃, treatment time 2~4 Hours. Although the effect of alkaline potassium permanganate treatment is not as good as that of molten salt treatment, its advantage is that it is suitable for assemblies with welds or curling.
Dipping method pretreatment To loosen the scale, the following strong acids are directly used.
Dipping pretreatment To prevent the acid from dissolving the matrix metal, it is necessary to strictly control the acid leaching time and the temperature of the acid solution.
Post time: Feb-15-2023