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How Does the Passivation of Aluminum Castings Reach More Than 360 Hours in the Salt Spray Test

How Does the Passivation of Aluminum Castings Reach More Than 360 Hours in the Salt Spray Test

How Does the Passivation of Aluminum Castings Reach More Than 360 Hours in the Salt Spray Test



With the continuous improvement of aluminum die-casting technology, the use of aluminum alloy die-casting has become more and more extensive. Then the passivation of aluminum castings can do these points, and the salt spray detection can reach more than 360 hours!


1. Die cast aluminium alloy materials with low silicon, copper, phosphorus, and iron impurities must be selected. Because the material contains impurities, the corrosion resistance of the die cast aluminium alloy is reduced. Its corrosion resistance will greatly increase the difficulty of the passivation process.


2. Firstly, the die cast aluminium alloy workpiece is sand-blasted, vibrated mechanically polished, and then cleaned with a cleaning agent. Mechanical polishing is beneficial to remove dirt, release agents and grease from the surface of the workpiece. Some mechanical polishing does not use detergent for cleaning, which is wrong. Because the mechanically polished polishing material is often greased and contaminated by the release agent, grease still exists on the surface of the polished aluminum casting. Failure to clean will affect the effective progress of subsequent processes.


3. Choose a scientific and reasonable process for die cast aluminium alloy.

For the passivation process that requires more than 360 hours of salt spray, we generally follow the steps of cleaning and degreasing, water washing, activation treatment, passivation treatment, drying, and packaging. The perfect process is the passivation process guarantee for the salt spray inspection for more than 96 hours, and it is one of the important links of passivation.


4. The passivation of aluminum castings must use a trivalent chromium passivation agent with good corrosion resistance as the passivation solution.


For example, the SY-40201 trivalent chromium passivation agent has better passivation and corrosion resistance. If it is additive passivation, it can reach more than 48 hours. The light blue passivation can be up to 360 hours, and it has good corrosion resistance.


After proper improvement of some process parameters of the passivation solution, the corrosion resistance of the conversion coating is improved, which in turn increases the salt spray detection time of die-cast aluminum. When passivating aluminum castings, we increased the concentration of the passivation solution to 15%, changed the original temperature soaking to heating soaking, and increased the passivation time to 5 minutes, so that the passivation process quality has a better guarantee.


If the material contains high silicon and copper, it can be passivated twice, and the salt spray can more than double. We use this process to solve many problems of high salt spray.


It is not a very difficult task for the passivation of die cast aluminium alloy to undergo salt spray treatment for more than 360 hours. It only needs to be handled in strict accordance with the above aspects.

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