Alodining of Assemblies

[smjmitchell]

Hello,

I wonder if someone with knowledge of the alodining process could comment on the advisability of alodining assemblies (as opposed to separate parts that are later assembled which is normal practise). What problems and issues are likely to be encountered ?

I have two scenarios in mind.
(1) Aluminium sheet parts assembled by riveting.
(2) Aluminium parts assembled by welding (stitch welds leaving the joint open to ingress of the solution).

Alodine 5992 will be used but comments about Alodine in general would be useful.

Thanks,

Steve

 

[TVP]

Al assemblies are coated with Alodine all the time. There are obviously issues that must be understood, such as those that you mentioned. The biggest issues with any coating operation are cleaning and rinsing. If the parts can be adequately cleaned and rinsed, then they can be coated. If the assembly leaves areas that cannot be accessed by the cleaning solution, then they won't be coated. If the parts are cleaned, but not effectively rinsed, same result. Assemblies tend to trap fluids, which means that cleaning chemicals may be transferred to the rinse tank, and so on down the line. This latter issue often results in residues forming that prevent good coating. Make sure you discuss your specific situation with a competent coating/plating supplier.