[juluq]

Hi,

Many years ago I was welding an exterior handrail set in concrete, and noticed a fire had started where the steel post met the concrete step. A sulfur deposit had formed and ignited. I have entered various queries involving "water", "iron", "sulfur", "concrete", "reactions", and have found nothing to explain this.
Could motor vehicle exhaust have caused this? It was a residential/industrial area.

Thanks
juluq

[Arkcon]

You question is a little hard to follow.  Lets try to get to the bottom of it:

Hi,

Many years ago I was welding an exterior handrail set in concrete,

OK.

and noticed a fire had started where the steel post met the concrete step.

I see fires started all the time, in campfire rings, ash trays, barbecue pits, fireplaces, etc.  People put stuff there and burn it.  Is that what you saw?

A sulfur deposit had formed and ignited.

So a sulfur fire?  Or a fire with sulfur?

I have entered various queries involving "water", "iron", "sulfur", "concrete", "reactions", and have found nothing to explain this.

I have to guess, from the context, that you think the sulfur and the fire came from the iron and the concrete.  But that's such an odd question, I have to ask you to ask it directly.  Its doesn't follow logically.

Could motor vehicle exhaust have caused this? It was a residential/industrial area.

Well, how close, was it an engine backfire or just driving down the road?  If the latter, then this should happen all the time, and it doesn't.

Thanks
juluq

Glad to help, but I think some kids were just playing with matches.  Or fireworks.  Or something.

[Enthalpy]

A vehicle exhaust doesn't deposit sulphur, it only emits tiny amounts of sulphur oxides which don't burn further and are gases.

Plain sulphur is sometimes used to repel dogs who urinate at posts.

What lets you tell it's sulphur? Smoke odour maybe?