Road salt on a galvanised platform ?

sarabande

sarabande

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Non-boaty, but techy...

The hydro-electric plant has a galvanised steel access platform which, this morning, was iced over, causing some excitement.

If I spread salt and grit (as used for roads) will that act adversely on the structural steelwork, causing it to corrode ?


Or should I just provide a bag of builder's sand ?

TIA
 
Galvanised steel seems to survive quite well in sea water so I'd go for the rock salt (which is what you see bing spread from the "gritting lorries) rather than sand. Rock salt will cause the ice to melt if fairly short order carrying much of the salt away with it. The sand will have little effect, will not disappear when the ice has gone and will need removing at some point.
 
Some salt on galvanized steel should not be a problem. Certainly it will hasten the corrosion, perhaps reducing what might have lasted for 70-80 years to 50 or so.
Typically a hydro plant is fresh water (and I'm assuming so in asserting the above) and the only salt would be your occasional ice breaker. Then the next rain will wash that off with fresh water
The most corrosive thing to galvanizing (zinc) in normal use are acids, and then sulphur containing compounds. Nationally, the introduction of low sulphur fuels has reduced the S in the atmosphere so much that the theoretical lifespan of galvanizing in an uninhabited country area is well over 100 years (extrapolated as 170 years in some places).
Many galvanized steel installations are in the sea, or (worse) the splash zone, and they last 15-25 years.
 
sarabande said:
Non-boaty, but techy...

The hydro-electric plant has a galvanised steel access platform which, this morning, was iced over, causing some excitement.

If I spread salt and grit (as used for roads) will that act adversely on the structural steelwork, causing it to corrode ?


Or should I just provide a bag of builder's sand ?

TIA
Click to expand...

As others have said, no problem using salt. Is it just a flat sheet of galvanised steel? Our marina pontoons are galvanised expanded steel mesh which is very non slip and as far as i have experienced so far stays nonslip even when frosty without salt so maybe if you bolted a sheet of galvanised expanded mesh on top you would always have non-slip without having to worry about applying salt in time.

Www.solocoastalsailing.co.uk
 
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The one problem I foresee is using grit based salt and people trampling on it will undoubtably cause a scratch that breaches the galvanising coat, then your problems will begin. A sand salt mix would be better.
 
petehb said:
The one problem I foresee is using grit based salt and people trampling on it will undoubtably cause a scratch that breaches the galvanising coat, then your problems will begin. A sand salt mix would be better.
Click to expand...

I see it a different way, the sand will act as an abrasive and help to reduce the galvanised coating over a larger area.. In the salt and scratch case I thought that the zinc ions flowed into the scratch and stopped the corrosion. The grit is not really abrasive grit like sand is abrasive.
 
Don't forget salt is only effective down to -6C. Round here (in France) temperatures get a lot lower and they only use salt on the roads if it's relatively mild, +3 to -6C. They use grit when it''s colder.
 
petehb said:
The one problem I foresee is using grit based salt and people trampling on it will undoubtably cause a scratch that breaches the galvanising coat, then your problems will begin. A sand salt mix would be better.
Click to expand...

I disagree also. Sand is definitely abrasive, much more so that salt.
Galvanizing gives electrolytic protection as well as barrier, so its not like paint (barrier only) where a breach will allow corrosion. Zinc surrounding a scratch with protect practically up to about 5mm width of scratch.
As galvanizing is zinc alloyed to the steel, it's pretty difficult to get it off other than slow corrosion - and that's what its designed for.
 
MM5AHO said:
I disagree also. Sand is definitely abrasive, much more so that salt.
Galvanizing gives electrolytic protection as well as barrier, so its not like paint (barrier only) where a breach will allow corrosion. Zinc surrounding a scratch with protect practically up to about 5mm width of scratch.
As galvanizing is zinc alloyed to the steel, it's pretty difficult to get it off other than slow corrosion - and that's what its designed for.
Click to expand...

Yes it will initially protect and that is exactly what the zinc does it sacrifices itself and it will do it quite quickly so the area around the initial scratch becomes quickly depleted of zinc and then the steel will begin to oxidise.
Neither option is good as you point out sand is abrasive but it is in the short term unlikely to breach the galvanising whereas the grit is likely to result in numerous small scratches through the protective coating which will then set up numerous galvanic cells depleting the surface coating. It was often the mode of failure of galvanised buckets. You pays your money and takes your choice.
 
Road grit/salt it is then :)

I am putting in a 240v pressure pump to de-ice any build up on the screw in winter, so we can quickly wash down gritty salt with fresh water.


Thansk everyone.
 
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