Sodium Iodide Nal - A lesson to learn

[Steven Sesselmann]

Hi Guys,

This morning when I went into my workshop, I discovered my lathe in a shocking state, it had rust all over and my hand tools near and around the lathe had the same problem. I immediately suspected an acid spill, but could not recall using any hydrochloric or sulphuric acid in recent times.

Then I remembered a little mishap the other day, when I was trying to separate a 1" NaI crystal from it's aluminum tube using the lathe. It came loose from the chuck and jammed, causing the crystal to chatter. I swept up all the debris and disposed of it, thinking no more of it.

This stuff is far more corrosive than I imagined, and the local weather being unusually hot and humid probably did not help.

I hope others as well as myself can learn from this.

Attachments 1-4: Photos of corrosion
Attachment 5.....: NaI(Ti) MSDS

Steven

[Doug Coulter]

Old gun-smithing books have a shop trick of using a little iodine (just about any compound) to permanently cause a screw to rust in place. Hope you didn't ingest much of this, the Tl isn't so good for you either.

[jcs78227]

Steve,

Yes, it looks like moisture was a huge problem. Hard to imagine if you cleaned up the mess straight-away that you'd see that amount of damage...I'm actually kind of shocked myself.

I guess it's a nice reminder to us how hygroscopic NaI crystals are and that when they do absorb moisture, molecular iodine is subsequently freed to corrode our valuable metal instruments.

Wouldn't be concerned with the thallium(I) iodide. Not particularly soluble and the amount of thallium present wouldn't make a lab rat ill, the iodine liberated is a different story.

-Jonathan

[Chris Bradley]

Doug Coulter wrote:
> Old gun-smithing books have a shop trick of using a little iodine (just about any compound) to permanently cause a screw to rust in place.

... seems to be in the books for under-body motor vehicle parts design, too!!!

(footnote: Scarily, some countries in Europe are now adding magnesium chloride to their road salt/gritting mix, because of its deliquescent properties. I suspect that includes a %age of MgI2 too.)

[Donald McKinley]

Steven,

How did you clean up the mess so that it doesn't continue destroying your lathe. I did a quick search and didn't immediately see a good way of dealing with the mess.

I would be concerned with an ongoing problem unless completely cleaned.

Don

[Steven Sesselmann]

Hi Guys,

According to the Material Safety Data Sheet (MSDS) from Saint Gobain that I attached at the bottom of the first post, the health issues with NaI(Ti) are minimal. Skin irritation etc, and possibly an issue if you get some of it in your eyes.

Fortunately very little of the debris ended up on me. After the crystal broke, I swept up the pieces with a small brush and a dust pan, and disposed of it in the garbage. The rust might have taken around 3-4 days to develop.

I cleaned up my lathe yesterday, by liberally spraying WD40 (Water Displacement oil) all over the affected areas and scrubbing with some steel wool. The surface is now rust free, but slightly pitted.

Steven

[DaveC]

Steve -

That's an unpleasant "learning experience".

Probably, needs an actual wash off with water, and detergent, followed by drying with paper towels, perhaps acetone and finally the WD-40 or similar water displacing agent.

The lathe ways can be gently cleaned with a new sharpening stone and kerosene (or WD-40) to get past the pitting. Need to go pretty lightly, however, so the surfaces stay planar. Silicon Carbide paper with oil and a straight backing plate will also work nicely. I'd suggest 320 grit or possibly 400. finish with 600 if the surface needs cosmetic improvement.

Dave Cooper

[Frank Sanns]

It only take the vapor from an acid to pit and rust the metal. Having a bottle of any acid within feet of steel is asking for trouble. Even the residue around a bottle cap of an acid is sufficient to travel quite some distance and do damage. The key is to keep all steel well oiled at all times to keep water off of the surface and the vapors away.

Frank Sanns