The workpiece surface sometimes attached to a layer of red precipitate after the oxidation treatment is, which is oxidized liquid used for a long time, have too much iron oxide caused by the solubility of iron oxide crystals in this less concentrated solution is very small, so the oxidation can precipitate on the surface of the workpiece, this kind of phenomenon can take the following measures to eliminate and prevention.
(1) To strictly control the working temperature of the blue solution. Bluing solution required working temperature in iron and steel with carbon content or without alloy composition as the basis. High carbon products, when the initial temperature and end point temperature and solution are low, and low carbon steel or alloy parts is opposite. Different kinds of steel products at the same time the blue, the time slot can be staggered, the first to deal with the high carbon content of the product, to be processed to the end point, the temperature of the solution is also up, just need to start parts of lower carbon content into the groove when the temperature. This can avoid the emergence of red cream.
(2) Take two times bluing process. The specific approach is: first part in solution formula of low working temperature of Bluing of about 15min, and then the solution to slightly higher than the normal operating temperature to blue 40-60min, the first solution tank temperature control at 130-135 DEG C, second tank temperature control solution at 140-150 deg.c (with different carbon content of the iron and steel products level). A crystal core is formed in the first groove, and then continues to grow in the second slot so as to form a dense and thick oxide film with high corrosion resistance.
(3) Increase the washing step parts of the bluing process. After the treatment of 5min in parts of Bluing tank, taken out from the groove, Mengchong in tap water, this time due to surface adhesion parts of the red frosting just formed, thin, easy to rinse, and then continue to appear less when blue red frosting.
(4) Add potassium ferrocyanide blue solution. Because potassium ferrocyanide can precipitate with ferric ion complex formation of Prussian blue, thereby reducing the iron ions in solution, reduce red precipitate appeared on the surface of parts, but the cost is higher and somewhat toxic.
(5) To strengthen the maintenance of blue solution. Strengthen the maintenance of blue solution is to prevent the emergence of one of the most effective method of hanging red cream, is the root of the problem, the red surface parts is frost which increased with high iron ion in the solution and to a certain extent, so when the price of iron ions in solution to accumulate a certain amount of Bluing needed to clean up, the specific method are as follows: adding the original volume of 1/4 in blue solution in the hot water, the dilution, and then heated to boiling (boiling temperature solution at about 120 DEG C), to be static suction tank bottom sediment in red basin (to be precipitated and the supernatant to bluing tank supernatant was concentrated), or quality the concentration of added material to make it consistent with formulation requirements, then the blue film surface will not appear red frosting. This method needs to be carried out regularly.
(6) Removal of sodium cyanide solution. Red frost formed on the surface of oxide film can be removed in sodium cyanide solution. After the solution treatment, the surface of the red cream can be completely removed, need to be noted that, after the event to strengthen the cleaning.
(7) Removal of finger by hand. This method is suitable for the large, blue and oiled after with a piece of soft cloth on the workpiece surface in order to gently wipe, red frosting will be removed with the cloth everywhere.