Sciencemadness Discussion Board

How to use a PT100 resistor in corrosive environment

Gargamel - 1-8-2022 at 07:33

Hi guys,

I'd like to use a PT100 to monitor processes where you expect a steel probe to get attacked.

You can buy glass covered probes, but I don't want to pay a lot of money.
Also a lot of European shops do not deliver to private individuals.

Something like a resistor in a hollow glass rod...

Would have a high thermal resistance, but still better than a probe outside the reaction vessel.

Do you have some proven home recepies?

unionised - 1-8-2022 at 07:44

The price sucks, but you could copy this sort of thing.
https://www.sigmaaldrich.com/GB/en/product/aldrich/z552445

Fulmen - 1-8-2022 at 10:20

Define corrosive. Epoxy or RTV can handle a lot of chemicals that would attack steel.

Gargamel - 1-8-2022 at 10:27

Nascent chlorine, diluted nitric acid... both at up to some 80°C...

CharlieA - 1-8-2022 at 14:09

Quote: Originally posted by Gargamel  
Nascent chlorine, diluted nitric acid... both at up to some 80°C...


If you have, or can get, soda lime glass you should be able to prepare a glass sheath for the probe. Or maybe narrow test tube could be used.

WGTR - 1-8-2022 at 14:23

A cheapo propane torch isn't usually enough to fuse borosilicate glass tubing by itself. However, I have found that it was still barely possible to fuse glass joints with propane preheating coupled with a small pin-point butane torch directed at the areas that needed fusion.

Or like Charlie mentioned, soda lime glass tubing is fusible with propane.

Rainwater - 1-8-2022 at 14:43

Soda glass tubes are easy to work with.
Just seal one end. It can be melted with a candles heat and purchased from most hobby shops

ManyInterests - 3-8-2022 at 19:09

As someone who has had a PT100 probe busted by being corroded by sodium chlorate synthesis (it was not very pure sodium chlorate. I still need to purify it) I also was looking for solutions to this problem.

My need is compounded by the fact that I plan on making picric acid in the future. As we all know, picric acid and metals generally do not like each other and they will form highly sensitive picrates and I want to prevent that at all costs.

I ordered this batch of borosilicate tubes off aliexpress: https://bit.ly/3QcW3p2

I have a rough estimate of what diameter my prob is, but the 6mm ID (7mm - 1mm thickness) should be sufficient to house my probe, as well as some good thermal paste to allow for accurate temperature reading.
Quote:
A cheapo propane torch isn't usually enough to fuse borosilicate glass tubing by itself. However, I have found that it was still barely possible to fuse glass joints with propane preheating coupled with a small pin-point butane torch directed at the areas that needed fusion.


Isn't propane hotter than butane? I think I did see videos on ampuling chemicals in test tubes using propane torches? That is what I plan on doing is closing off one end with a propane torch. Even if it doesn't fully cover the thermal probe, I never had to fully immerse it in any solution, so I can just secure the other end with electrical tape and it should be OK.

Twospoons - 3-8-2022 at 19:32

I've used a MAPP torch to soften and fuse borosilicate successfully.

Gargamel - 5-8-2022 at 11:39

Thank you for the input :)

Glassrod it shall be.... Lets see what I can shop...

Oxy - 5-8-2022 at 11:46

I am using a sealed glass Pasteur pipette. It's torched on one side, on the bottom I put a tiny amount of silicon oil (for better heat transfer).
On the other side it's protected by electrical tape. This is very easy to setup with any lab burner and Pasteur pipette fits the thermometer adapter.

CharlieA - 5-8-2022 at 14:24

Quote: Originally posted by Oxy  
I am using a sealed glass Pasteur pipette. It's torched on one side, on the bottom I put a tiny amount of silicon oil (for better heat transfer).
On the other side it's protected by electrical tape. This is very easy to setup with any lab burner and Pasteur pipette fits the thermometer adapter.


Shade tree engineering in the chemistry lab! I love it!:D