Corrosion and pitting STC probe

[captsensible23]

Hi,

I've been using my regular STC 1000 to control fermentations in my fridge. In the past I've just been taping the probe to the side of the fermenter with some stubby holder insulation.

Just recently I have purchased and installed a 100mm thermowell. During the current batch I've noticed the metal end of the temp probe show signs of pitting and corrosion. It also has green spots on it (similar to green copper).

Do I need some kind of metal heat paste in between the two points of contact to stop this?
I've read something about the resistance of the metal relates to how the temp probes work, but I am thinking this maybe the course. As of now I'm not sure if this is gonna throw off temp measurements.

Anyone else had this problem? or know anyway to prevent this from happening in the future.

Cheers

 

[Camo6]

All of my stc probes are plastic. By the sounds of it, yours is metal? If so I doubt it's stainless and a reaction is probably taking place between the two dissimilar metals. Is any moisture getting in the thermo well? Heat sink paste would work but it's pretty toxic and I'd avoid using it.

 

[captsensible23]

Yeah it is metal. I'll shop around for a waterproof probe. save mucking around with the paste.

As for condensation, that would be the most likely cause. It has gone through fermentation at varying temps and several cold crashes.

Thanks

 

[Lyrebird_Cycles]

You can just fill the well with silicone, commonly done in industry. Slows the response down a little but for a fermenter that will not be a problem.

The common form of heatsink paste is zinc oxide in silicone oil and is not toxic. I believe the reputation comes from older pastes which used toxic ingredients like PCB.

 

[homebrewkid]

You can get cheap replacement temperature sensors on ebay

 

[TwoCrows]

I wrapped my probe in duct tape . The STC probe that is........

 

[captsensible23]

You can get cheap replacement temperature sensors on ebay

I've had to replace the original probe as it came with a 1metre one and was way too short to be useful. I'll look for a rubber one that states its waterproof.

 

[kaiserben]

When I was buying sensor probes for a temp controller I was building I remember seeing heat shrink wrap for sale (to water proof the probes).

I didn't bother buying, but I'm pretty sure it was very cheap. And the heating machine thingy to make the stuff shrink wasn't particularly expensive either - just not worth the effort when the probes themselves cost me $3.57 each delivered.

 

[abyss]

I put heat shrink tube over mine.

 

[klangers]

Sounds like the probe is made from chrome plated bronze or brass.

Chrome plated brass or bronze is generally fairly rubbish at not corroding in wet areas.

I just use the original (plastic) probe and that's perfectly sufficient. A waterproof one is probably the go -thermowells don't really add much value if you're constantly attaching/detaching from the fermenter.

 

[captsensible23]

Cheers. Seems like I cannot find any replacement rubber ones. I've owned several STC's over the years and they have all been the metal - chrome plated kind

 

[TheWiggman]

If it's corroding then moisture is the cause, and as Klangers said cheap coatings will accelerate this.
Some thermal paste from Jaycar will provide some protection but like you say, can be a bit sticky and messy. Alternatively a water dispersant (guess what WD in WD40 stands for?) will greatly slow corrosion.

 

[kaiserben]

This was what I bought (already with heat shrink wrap around it) 1.08m supposedly stainless steel and already water proofed for AU$3.70 delivered: here.

I also took note that they are selling 2m, 3m, 5m, 10m, 15m for between AU$10.13 to AU$12.85: here.

Free delivery (I think it took a few weeks to arrive).

 

[Camo6]

If it's corroding then moisture is the cause, and as Klangers said cheap coatings will accelerate this.
Some thermal paste from Jaycar will provide some protection but like you say, can be a bit sticky and messy. Alternatively a water dispersant (guess what WD in WD40 stands for?) will greatly slow corrosion.

As another aficionado of useless knowledge I can confirm that that 40 stands for the number of attempts it took the creators to achieve the right "recipe" for their dispersant.

 

[peteru]

If you are considering stuff like WD40, you might want to check out INOX products, which are available in food grade formulations.

 

[billygoat]

This was what I bought (already with heat shrink wrap around it) 1.08m supposedly stainless steel and already water proofed for AU$3.70 delivered: here.

I also took note that they are selling 2m, 3m, 5m, 10m, 15m for between AU$10.13 to AU$12.85: here.

Free delivery (I think it took a few weeks to arrive).

The STC1000 uses a NTC10K probe, those you linked to are DS1820B, different animal.

 

[captsensible23]

The STC1000 uses a NTC10K probe, those you linked to are DS1820B, different animal.

That explains why I can't really find rubber ones. I was searching ebay for 10k ntc, and they are all metal.

 

[billygoat]

That explains why I can't really find rubber ones. I was searching ebay for 10k ntc, and they are all metal.

I wouldn't bother too much about a small amount of pitting on the end of the probe. Its a metal sheath only, the NTC10K is a small resistor inside of the sheath. If it hasn't corroded through it won't throw your temps out. Give it a clean with a green kitchen scourer to remove the corrosion. Its sitting in a thermowell so won't affect your beer.
If you really want to replace it, buy another STC1000, as most have the plastic probe, use the probe and then you'll have a spare STC if one goes belly up.
If the wire on the probe isn't long enough you can solder on more wire. As long as you get a half decent joint it will work perfectly.

 

[captsensible23]

Cheers. I actually do have a replacement coming for the same fridge. Thanks for the info, explains why there were alot of resistors in the searches. I've got plenty of the same cable from recent purchases I can use if any thing is not long enough or goes belly up.

Thanks

 

[kaiserben]

The STC1000 uses a NTC10K probe, those you linked to are DS1820B, different animal.

Ah crap, sorry, I'd bought them for a Pi controller project. Got a bit mixed up with all the different controllers I'm playing with at the moment.

My Grainfather controller has a stainless sheath (and the controller is an STC200, which I've since replaced with a flashed STC1000.