PROBLEM OF COAL DUST ON Al AND GALVANISED STEEL ON MARINE ATMOSPHERE

[rinu]

Dear all,

We had a project in Portugal sea side for LNG terminal. Light coal from Indonesia is currently unloaded in Sines(Portugal) harbour. We were told by the client that this coal dust is aggressive specially for aluminium and galvanised steel. Does anybody know about risk of corrosion from coal dust?

 

[ccfowler]

It seems possible that a combination of sulfur in the coal and ambient humidity may be at the heart of the problem. Very dilute concentrations of sulfuric or sulfurous acids can produce quite severe corrosion rates.

 

[kenvlach]

The sulfur likely contributes in the manner pointed out by ccfowler.
Biggest effect is probably destruction of the passive protective layer on the metals due to galvanic corrosion in the presence of moisture, especially seawater mist with a little acid thrown in. Coal is probably very similar to graphite in its galvanic potential, meaning it is nobler than everything except gold and platinum.

For aluminum, you might try hard anodizing (with dichromate seal).
For steel, try a hot-sprayed ceramic coating.