Titanium alkaline washing capacity is burning on fire, especially the alkaline washing of titanium sheet is more likely to catch fire. The causes and mechanisms of alkali-washing of titanium are still under discussion.
The chemical activity of titanium in lye, when it is alkali-washed in molten alkali containing oxidant, the overall lye temperature is too high or the local temperature is too high, which is the original flash of titanium burning. Many studies have pointed out that due to the potential difference between titanium and steel tools (alkaline washing frame) in molten alkali, there is a galvanic effect. When titanium is in contact with steel, a galvanic current is formed, and the smaller the contact point, the higher the current. Big. The excessive current density at the contact causes local overheating, so that the titanium alloy often begins to burn from the point of contact of the two metals.
In order to prevent and reduce the ignition of the titanium pipe during alkaline washing, the following measures can be taken:
(1) Select a reasonable alkali lotion composition. The test indicated that (85%-95%) NaOH+(15%~5%) NaN03 alkaline washing solution was better.
(2) Strictly control the temperature of the lye. In the alkaline solution of the above ingredients, the temperature should be strictly controlled, whether it is whole or partial, it should be strictly controlled within the range of 480-520T/.
(3) Insulating the alkali washing frame with a high temperature resistant coating or a high temperature resistant insulating gasket. If the stainless steel alkali washing frame is used, the ceramic strip or the ceramic piece can be padded to separate the titanium material from the steel frame, so as to avoid fire.
During the alkaline washing process, the lye is continuously carried away or evaporated by the workpiece, so it is necessary to replenish the lye. When lye is replenished, the composition of NaOH and NaN03 should be analyzed periodically and adjusted as appropriate to keep the lye component relatively stable.
When the alkali is washed, the insoluble scale slag is deposited at the bottom of the tank, which affects the good thermal conductivity of the tank, and the gap caused by the precipitation makes the steel tank susceptible to electrochemical corrosion and greatly shortens its service life. Therefore, it is necessary to clean up the sediment in time. It is a common practice to use a movable trough to collect slag. When you need to eliminate deposits, simply hang the bottom of the active trough.