There are generally three types of stainless steel seamless pipe pickling and passivation
General solution for stainless steel seamless pipe pickling and passivation
(1) Pickling passivation drug HNO3 6% ～ 25% + HF 0.5% ～ 8% (volume fraction)：
temperature 21 ℃ ～ 60 ℃; time as required; or drug ammonium citrate 5% ～ 10% Molar mass); temperature 49 ℃ ～ 71 ℃; time 10min ～ 60min.
(2) Passive treatment drug HNO3 20% ～ 50% (volume fraction):
temperature 49 ～ 71 ℃; time 10min ～ 30min; or temperature 2l ～ 38 ℃; time 30min ～ 60min; or drug HNO320% ～ 50% + Na2Cr207H2O 22% ～ 6% (molar mass); temperature 49 ℃ ～ 54 ℃; time 15min ～ 30min; or temperature 21 ℃ ～ 38 ℃; time 30min ～ 60min.
(3) Descaling and pickling passivation drug H2SO4 8% ～ 11% (volume fraction):
Temperature 66 ℃ ～ 82 ℃; 6 inches 5min ～ 45min; HNO3 6% ～ 25% + HF 0.5% ～ 8% (volume fraction); temperature 21 ℃ ～ 60 ℃; or HNO3 15% ～ 25% + HF l % ～ 8 (volume fraction).
Plaster solution
(1) HNO3 25% ~ + 4% HF + 71% condensate (volume fraction) and BaSO4, adjust to thick. Passivation paste: 30% HNO3 or 25% + 1% HNO3 (molar mass) K2Cr2O7 and BaSO4 are adjusted to be thick. Apply the surface layer for 5 to 30 minutes, and wash it with condensed water to pH = 7. For each machine and equipment, an organic chemical passivation treatment by spraying hydrogen peroxide can also be used.
(2) Pickling passivation paste: HNO3 8% ～ 14% (as passivation agent); HF 10% ～ 15% (as corrosive agent); magnesium sulfate 2.2% ～ 2.7% (as emulsifier) magnesium nitrate 60% ～ 70% (as a filler to improve adhesion and hydrophilicity); sodium polyphosphate 2.3% to 2.8% (as a corrosion inhibitor); water (adjust viscosity).
Electrochemical method
Solve the problem of anodizing the stainless steel pipe parts waiting for review, and manipulate the potentiostatic potential to carry out anodizing treatment, or use stainless steel seamless pipe steel parts as the negative electrode first, and manipulate the potentiostatic difference to carry out cathodic treatment.
Then the stainless steel seamless pipe steel was anodized, and the potentiostatic potential was manipulated to perform anodizing treatment, and the potentiostatic difference was changed again to perform stainless steel passivation. The electrolyte solution was HNO3.
After that, the coating properties of stainless steel seamless pipes are improved, and the corrosion resistance is further improved. The crevice corrosion threshold potential difference (Eb) is increased by about 1000 mV (in 3% NaCl), and the resistance to uniform corrosion can be improved by three orders of magnitude (in 20% -30% H2SO4 at 45 ° C).
