Poor cleaning:
After chemical cleaning of the surface of the aluminum profile there will be pollutants or stains, which is caused by no uniform etching, when uneven etching, the surface of the aluminum profile will appear uneven or uneven color, showing different color spots after coloring. This is due to more oil on the surface of the aluminum profile, chemical cleaning work is not done in place, such as the temperature of the bath is too low, time is not enough, the effective ingredients are not enough and there is no timely addition of cleaning agents.
Countermeasures: regularly analyze and adjust the composition of the tank liquid, check whether the temperature of the tank liquid is within the specified range, add cleaning agent in time according to the use needs, so that the content of the effective ingredients in the tank liquid is controlled within the normal range.
Snowflake corrosion:
On the high side, when the content of zinc in aluminum in sulfuric acid chemical cleaning, zinc bath and the reaction of sulfuric acid and chloride ions in the crystal of aluminium profile surface snow pattern, also calls the snowflake corrosion, some parts will form a glowing pear skin, is due to the aluminum containing zinc, different grain boundary and grain orientation cause different dissolved quantity and cause, This occurs only in washing and alkali etching, but not in washing after nitric acid ash removal.
Countermeasures: reduce the content of zinc in aluminum profiles, control the content of sulfuric acid and chloride ions in the water washing tank, the content of zinc is controlled below 0.015%, the pH value of water washing should be greater than 3.5, the content of chloride ions is controlled in 15μg/g.
