(1) Chemical method
Concentrated nitric acid HN03 1000mL
Sodium chloride NaCl 40g
Temperature 65～750C
Speed ​​about 6μm/min
Precautions:
After the unqualified low-tin bronze coating is removed, the underlying metal surface is smooth and does not require polishing, but the process conditions must be strictly controlled;
2 All use concentrated nitric acid, can not have water, to prevent the substrate metal corrosion;
3 temperature can not exceed the process conditions, part of the base metal iron is corroded;
4 The chemical method can remove nickel, zinc nickel, copper, copper-tin alloy plating, etc. It is fast, low cost, and effective. Due to gas evolution, ventilation equipment is required.
(2) Electrochemical method
Triethanolamine [N(CH2CH20H)3]
60～70g/L
Sodium hydroxide (NaOH)
60～75g/L
Sodium Nitrate (NaN03)
15～20g/L
temperature
35～50°C
Anode current density
l. 5 to 2.5 A/dm2
Anode movement speed
20～25r/min
cathode
Iron or stainless steel plate
speed
About 20gm/h
Electrolytic method to remove the coating, the current should not be too large, the temperature should not be too high to prevent the corrosion of the base metal iron.