Selecting a conformal coating

[Psi]

What's a good general-purpose conformal coating to ask the PCB fab for?
Something that's provides moisture protection but doesn't cost too much.

The PCB is automotive but given it's location it will not be subjected to any solvents.
Moisture/humidity is my only reason for getting a conformal coating. 

Any suggestions?

I'm thinking Acrylic?

[tszaboo]

If you want to outsource it, just ask them what they usually use.
They will have a standard material, and if you dont have any special requirements, that will be OK 90% of the time.
Otherwise if you are not happy with the result, ask for something UL listed.

[coromonadalix]

chemtronics konform ar    can't recall how much a can cost

[Niklas]

What is the maximum operating temperature? Some types of coating are not suitable above +85'C.

[jkostb]

I have used in past mainly conformal coatings from Humiseal (e.g. UV40-250, 1B93 etc). Some coatings need to be sprayed once, other need to be applied in 2 layers. Please have a look at website of Humiseal. Most PCA assembly houses use standard one type of coating. Switching to other type means flushing machines etc. So you better ask your production facility what the default coating is they use.

[Niklas]

What is the maximum operating temperature? Some types of coating are not suitable above +85'C.

Some requirements from an automotive customer:
Above +85'C, (ER) Epoxy, (SR) silicone and (XY) Parylene accepted
Below +85'C, (AR) Acrylic, (ER) epoxy, (SR) silicone, (UR) urethane and (XY) Parylene accepted.
And a note that silicone coating is not recommended for applications with possible high amounts of sulphur vapors as it can be aggressive on silver and damage components.

[Psi]

Thanks.

One of the chips may get over 85C if the ambient temp is really high.