Sciencemadness Discussion Board

Curious corrosion formation

Twospoons - 9-3-2016 at 18:23

We're carrying out salt fog corrosion tests at work, and one of the test pieces has produced these weird little tubes, like little trumpets about 2mm in diameter. The substrate is zinc plated steel, and the little tubes grew over several days during the rest phase - that is out of the fog chamber and sitting on the bench at room temperature. Humidity here sits around the 60-70% mark.
Anyway, I just thought they were interesting.



corrosion.jpg - 222kB

Daffodile - 9-3-2016 at 20:42

Kill it with fire before it lays eggs?

BromicAcid - 9-3-2016 at 20:43

That is pretty awesome, thanks for sharing.

deltaH - 9-3-2016 at 22:21

Spectacular!

NeonPulse - 9-3-2016 at 22:41

That is pretty cool. Any ideas on how they formed such strange shapes?

wg48 - 10-3-2016 at 03:30

Those forms are super awesome.

I have seen bubbles of corrosion products (rust) on steel. Possibly caused by a blob of condensation initially forming then insoluble corrosion products deposited at the surface of the blob.

Perhaps in your case the corrosion products are deposited at the edge of the blob forming a ring. As the ring grows it forms a tube or trumpet if the diameter increases with growth.

The floor of my shed tends to be cold (possible a little damp too) steel objects left on the floor sometimes develops those bubbles of rust. But they occurs in just a few points on the steel. Possibly where a protective coating fails. Perhaps the initial corrosion products are deliquescent so an initially microscopic spot grows while the rest of the steel remains free of condensation. I will have to check for trumpet forms now.

I suggest you save some specimens of your steel and documents the conditions. Can you take a time lapse video of the growth? You could post it on Youtube with a provocative title along the lines of a metal eating fungi LOL.

Morgan - 10-3-2016 at 07:54

They might be called tubercles.
http://ecscorrosion.com/galvanized-pipe-vs-black-steel/

[Edited on 10-3-2016 by Morgan]