Sealed layer on type III hard anodize

[Cole Hanson]

Hey all,

We have a shaft that gets a Type 3 class 2 hard ano with a nickel acetate seal. These shafts then get a grind/polish operation to bring them into diameter spec and surface finish spec (8-10 Ra micro in). I have a batch that has a tacky sensation on the surface, and is causing some noise in the assembly and I am correlating the noise to the tacky sensation. The question is if the grinding operation which removes up to 0.0003" per surface is removing enough material to get below the sealed layer, or if the seal was poor in the first place. Or, if there are any other causes for this type of tacky sensation that anyone is aware of.

Thanks!

 

[chez311]

Nickel Acetate seal does not cause any dimensional change - my understanding is that it essentially "fills in" the pores left by the anodizing process. Can you seal after polishing/grinding? Or eliminate the use of a seal at all (depending on your corrosion requirements)? There are also other options for sealing anodized coatings. Perhaps there is an interaction with the dye as well - could you use a class 1 non-dyed coating? I would check what type of wheel they are using to grind/polish the surface - I don't know what is proper for gridning/polishing this type of coating but perhaps some conversations between your grinding/polishing vendor and coating vendor would be in order.