What is the potential damage to multi-strand stainless steel wire from ferrous oxide (FeO) powder in fine dust

Question

A huge excavation at a construction site upwind and very near the marina where I keep my sailboat is putting out a lot of very fine dust that contains ferrous oxide. This stuff is coating every surface of the boats. What are the potential damages to stainless steel and aluminum fittings on our boats?

Answer 1

The trouble is that when the iron dust settles on the metal, the dust can be oxidized to form microcrystals of rust. Once the dust has become rust, this can start a chain reaction that eats into the steel and induces the steel to rust. Normally stainless steel avoids air oxidation, but it is succeptible to chemical oxidation. You may be tempted to think that if the steel can resist water corrosion, then it can resist this kind of attack too, but these solid microcrytals can cause miniscule, invisible scratches in the surface of the metal that slowly promote the growth of rust veins.
The aluminum is safe. The surface of your aluminum fittings is already totally oxidized to aluminum oxide, which unlike rust, is safe and strong. Oxidation damages iron, but it makes aluminum stronger.
You need to clean this stuff off as quickly as possible. Even if you do not see rust, you might start to see it later, even as long as a year from now or later.
If you have any kind of corrosion-resistant oil or coating that you can put on the steel, clean the steel first. Do not apply the coating over the iron oxide dust. This will actually accelerate corrosion.
There are no special cleaning precautions. A brush works fine. If the fittings are small, a toothbrush or a very soft copper brush is ideal.

Answer 2

I think that this is potentially rather nasty.

FeO will further oxidize and form hard abrasive crystals. I don't think that they will do any chemical harm to aluminum.

The problem is with the stainless steel, it can be persuaded to rust if it is scratched with these crystals so it does need to be cleaned off, high pressure air may be best. Protect the steel with a suitable grease coating that you know you will be able to remove with a safe solvent later.

The real problem comes with any stainless rigging. As the rigging moves and works, the dust and small crystals will work in between the strands, scratching them and possibly persuading them to rust. It will be a rather tedious job but once again cleaning very carefully with high pressure air and then protecting with a suitable grease coating should do the trick.

You might want to find out exactly what it is that they use to protect stainless and other steels during storage and shipping.

Answer 3

Hi. Worst case? If the iron made the correct mixture with the aluminum you could wind up with thermite. Do a search.