FKM gasket stick to anodized AL base 1

[Mox-TT]

Hi,
I got problem that FKM seal will stick to anodized aluminum after 9 days` chamber test(-30degree 5%humidity for 72h,40degree 90% for 72h, 60degree 5% humidity for 72h).
This lead to failure of movement for armature.
Any guys know the reason of this stick issue and how I can avoid this problem?

https://files.engineering.com/getfile.aspx?folder=4af5bc4f-c6cd-410b-aabd-9848a07dedcf&file=1.jpg

https://files.engineering.com/getfile.aspx?folder=4d24d2f1-f5bc-4ec8-84d0-cc1e46c23af5&file=2.jpg

https://files.engineering.com/getfile.aspx?folder=76cc1fe3-1f40-43ab-8364-3050bd38d732&file=3.jpg

 

[3DDave]

Which picture shows the surface that the material is sticking to? Labeling the items might help.

It's possible the anodize wasn't properly sealed following the anodize process but it may also be that the material was incompletely polymerized and is simply gluing itself to the surface.

Does this form a seal in a liquid handling system? If so what is the liquid?

 

[Mox-TT]

1st pic showed rubber stick to AL. You can see armature did not fall off under gravity.

Pic 3 showed appearance of sealing rubber after contacted with AL under pressure of solenoid spring.

This solenoid is normal closed, FKM seal is to seal this hole. There is only air in base. Power on the solenoid will let armature move and gate will open, air can flow then.

Your opinion that "anodize wasn't properly sealed following the anodize process" may cause stick issue, maybe no any surface treatment on AL will be better for this case.

 

[TugboatEng]

Are you using aftermarket parts? The rubber seats aren't usually black on these valves. They are normally green or blue which may indicate a PTFE coating.

 

[Mox-TT]

Hi, TugboatEng
Yes, we purchase this solenoid and assemble it to AL base. PTFE coating on trading part may not be good since it need be sent out and processed agian.

 

[btrueblood]

You might ask about the processing history and makeup of your "FKM". Specifically, what curing system was used, whether any post curing (bakeout) was performed. You should purchase seals from a shop that does their own masterbatch and mixing, and controls the process of molding the rubber, so that they can then advise you on what changes to formulation, cure, and post-cure processing would reduce the adhesion problem you are seeing.

Or you could wipe the surface of the seal with a bit of silicone grease before assembly, and see if that eliminates the adhesion problem.

 

[btrueblood]

It is strange that you are using an expensive fluorocarbon elastomer if the seal only ever sees air...

 

[TugboatEng]

These DC solenoid valves run hot. If continuously energized the seal will have taken significant compression set after only a few years of operation.

 

[Mox-TT]

Hi, btrueblood
We are planning to add silicone grease on rubber and heating the assembly in chamber to see if it can eliminate the adhesion problem.