coating on MK20 spring

[dinogep]

In one of the old MK20's the main spring was coated with a semi-transparent layer of plastic, that was soft enough to scratch with a fingernail, and flaking in places. I have decided to remove it with a brass brush, but I do not completely understand the original purpose of the coating. Most of the springs in regs I have seen did nicely without an anti-corrosion coating, and the flaking on this one seems downright dangerous...

 

[redacted]

I believe it was part of the TIS (thermal insulation system/) features and was supposed to help shed ice.

 

[dinogep]

wow. One other function I did not think of. Do you know how effective it was, or whether it is a good idea to try to recoat the spring with some soft resin or something?

 

[redacted]

I am a WWW (warm water wuss) so have no idea on effectiveness but I suspect the right answer is a sealed ambient chamber if ice is a threat. I doubt if there is any real value in replacing or recoating.

 

[dinogep]

For ice diving I normally use a Mares MR22 and an Oceanic FDX10, the MK20's were reserved for stages for cave diving. Maybe I try them next weekend in the lake, the surface is frozen now for a week so it will be crystal clear down under.
My method for testing is to stay at the end of the dive right under the ice and breathe really hard for a minute or two, then press the purge. If it does not freeze open, it is OK.