We are trying to get a sol-gel film coating on diecast aluminum/silica (87%/13%) parts, and it is flaking off quite rapidly. This same flaking isn't happening with prototype milled aluminum parts. At the recommendation of one expert, we're paying closer attention to surface preparation; we've changed our sandblast process, washing in an alkali bath, heat treating to remove any surface impurities (300C for 1 hr), and built fixtures to keep parts from being set on surfaces. There is a primer coat and top sol-gel coat that are supposed to be compatible with aluminum, but it's still giving us issues.
Is surface impurity from the die-cast process the likely culprit here, or do you believe it could be a materials/process issue?
Thanks in advance!
Dear Dr. Jerrod Keith ,
a very interesting question.
I suggest you to have a look at the following documents:
- Resolving Adhesion Problems in Post Die Casting Operations by Lauren Campbell (2016)
Available at: http://www.hillandgriffith.com/blog/bid/398239/resolving-adhesion-problems-in-post-die-casting-operations
-Surface finishing for die casting – Bulletin N. 4 (1996)
Available at: https://cwmdiecast.com/wp-content/uploads/2020/04/NADCASurFin4DC.pdf
- Polymer bonding and adhesion on aluminium and magnesium alloys by F.M. de Wit (2012)
Available at: https://tinyurl.com/y3elmbsy
My best regards, Pierluigi Traverso.
Dear Dr. Jerrod Keith ,
a very interesting question.
I suggest you to have a look at the following documents:
- Resolving Adhesion Problems in Post Die Casting Operations by Lauren Campbell (2016)
Available at: http://www.hillandgriffith.com/blog/bid/398239/resolving-adhesion-problems-in-post-die-casting-operations
-Surface finishing for die casting – Bulletin N. 4 (1996)
Available at: https://cwmdiecast.com/wp-content/uploads/2020/04/NADCASurFin4DC.pdf
- Polymer bonding and adhesion on aluminium and magnesium alloys by F.M. de Wit (2012)
Available at: https://tinyurl.com/y3elmbsy
My best regards, Pierluigi Traverso.
B. E. Watts , the prototype sandblasted parts to this point all flake. We thought that the sandblast would remove all mold release and surface contaminants, but it seems that isn't the case. We've modified our procedure to include more surface pretreatment (heat treat, alkali dip, etc., mentioned in the original post), and more prototype parts are in process.
@Pierluigi Traverso, thank you for the papers! I am printing them now. I very much appreciate it!
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