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Preventing red Exo-frost on the surface oxide film?
Dec 07, 2016

Work surfaces are sometimes attached to a layer of oxidized red precipitate, which is oxidized liquid used for too long, caused by accumulating a plethora of ferric oxide, this smaller crystals of iron oxide solubility in concentrated alkaline solution is very small, thus the oxidized surface when precipitation, may take the following measures to eliminate and prevent this phenomenon.

(1) strictly control the bluing solution temperature. Bluing solution temperature required is based on the carbon content of steel parts high or low or no alloy composition is based on. Workpieces with high carbon content, bluing solution when the starting temperature and end temperature is lower, and products with low carbon or alloy steel parts, on the other hand. Different types of steel parts and blue at the same time, time to stagger the first slot to handle workpieces with high carbon content, to be processed when it reaches the end, the temperature of the solution up, products starting with a lower carbon content in exactly the temperature you need into the slot. So as to avoid the appearance of Red Exo-frost.

(2) take bluing process II. Approach: parts in low temperature solution formulations for blue 15min, and then move it to slightly higher than the normal operating temperature of the solution continues to 40~60min blue, the first tank temperature control in 130~135℃, the second tank temperature control in 140~150℃ (with high and low carbon content in steel parts). Parts formed nuclei in the first slot, and then continue to grow in the second slot, connecting it to the film, resulting in dense and thick oxide film with high corrosion resistance, but also greatly reduce red Exo-Frost appeared.

(3) Blue increases workpiece processing steps in the process. Workpieces processed in a bluing tank 5min, remove it from the slot, under the tap and dashed out, at this time because the surface adhesion red Exo-frost had just formed parts, thin, easy to rinse, then go red Exo-frost on bluing when less will appear.

(4) add tetrapotassium hexacyanoferrate bluing solution. Because of tetrapotassium hexacyanoferrate Prussian blue precipitate with ferric ions complexing generated, so as to reduce the content of iron ion in solution, reduce red sediments on the surface appearance of parts, but this cost is slightly higher and slightly toxic.

(5) strengthen the bluing solution maintenance. Strengthening blue solution of maintenance is prevent appeared red hanging cream most effective of method one of, is root of method, parts surface red hanging cream in must degree Shang is with blue solution in the high iron ion of increased and aggravated of, for Dang blue solution in the accumulation must volume of high iron ion zhihou need for cleanup, specific method following: first in blue solution in the joined original volume 1/4 of hot, makes of diluted, then heating to boiling (at solution of boiling point temperature about 120 ℃ around), Wait for the static suction slot red sediment in the basin (supernatant after sedimentation bluing tank), the supernatant is concentrated or additional materials to make it meet the requirement formula quality concentrations, then blue films does not appear red Exo-frost on the surface. This method often.

(6) remove sodium cyanide solution. The Red Exo-frost has formed on the surface oxide film can be soaked in a solution of sodium cyanide dropped. Processed by this solution, red Exo-frost on the surface of the workpiece can be completely removed, is in need of attention, to enhance cleaning.

(7) manual clean removal. This method is suitable for large, having blued and oiled with a piece of soft cloth on the surface of workpiece in order to gently wipe, red Exo-frost will follow where velvet would be removed.