Water Stain Mark Improvement
We have come across many challenges in surface cleaning, one of the common scenarios is the
work piece get dry off before the detergent comes into the cleaning roles. The dry-off area will becomes a stain mark as a general term.
In our pass experience, we definite do not want to work against stain marks which dry off at the work surface, especially a dry surface on a precise aluminium surface.
Why A Dry Water Stain Mark is Not Preferred?
Water stain mark is happening in regard to pool control. For a demanding process, the process owner should consider way how to reduce and eliminate the dry-off water stain mark.
In practical cleaning process, dry-off stain mark is definitely not easy to clean unless an aggressive removing method is introduced. The contaminant will adhere on the piece part surface with Van der Waals’ force. The Van der Waals’ force is magnified under micro structure.
Field engineer shall introduce detergent and scrubbing force in order to remove the dry-off stain mark, however the force is enormous and very challenging to remove. Base on our experience, the stain mark is hard to totally removed. Moreover, you are most likely to see some crack or trace mark left over on the surface, perhaps this is some sort of a corrosion effect.
How to improve from the Stain Mark situation?
The whole concept for removing dry-off stain mark is to prevent it from happening. There are several concept field engineer could adapt through-out the process.
- Reduce the work piece dry off possibility after the wet process. During a wet process, field engineer should ensure the work piece always stay at wet stage through-out the process. Dry off definitely is not acceptable as the contaminant will be easily adhere on the work surface.
- Soak the work piece in a detergent solution right after the wet process. Transferring the wet work piece and merge in detergent is mandatory while it is under WIP stage. The detergent will act as a repellent to prevent contaminant adhere on work piece. After that through PVA sponge roller or PVA brush, the contaminant could easily be removed.
- Reduce bubble formation. Bubble is easily generated with difference surface tension. Field engineer shall ensure the bubble is not dry-off before it merges into detergent solution. Any dry-off bubble will be a source of stain mark.
Stain Mark Removal.
For those dry off stain mark, we could remove it with 2 methods:
- Mechanical polish. Using mechanical brush is one of the common ways for stain removal, unfortunately this method may bring severe damage on the piece part surface. We have more choices if we only encounter a minor thin film of stain mark attach on the metal surface. Select a suitable grinding stone or polishing pad, roll over the grinding stone on the metal piece part, the minor thin film of stain mark could be removed. You could also adding some abrasive further enhance the removal effectiveness.
- Chemical Polish. Chemical polish is another common method if you want to get an uniform surface. For metal surface, most of the chemical polish solution is mainly formulated under phosphorous acid base but we could use alkaline base in certain condition. Unfortunately for aluminium base metal, the choice is constraint because the chemical polish solution can easily corrode the surface. Detergent solution could consider as one chemical polish solutions but the effect is mild. In this case, normally we do not expect a detergent is able to remove the dry off stain mark effectively.
Field engineer should take the cleaning process as a whole while come to stain removal. Again, the best improvement way for removing the stain mark is preventing it from happening.