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Corrosion? happening on galvanized steel

Corrosion? happening on galvanized steel

Corrosion? happening on galvanized steel

Do you think corrosion is happening on these galvanized steel plates with a low level corrosion resistant coating (G90)?
They were sprayed by a solution(Sodium hypochlorite, Sodium carbonate, Sodium hydroxide) one year ago.
(The surface was shiny before the spray.)

RE: Corrosion? happening on galvanized steel

It is doing what it is supposed to, the Zn is corroding to protect the steel.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

RE: Corrosion? happening on galvanized steel

Why were these plates sprayed with that combination of chemicals?

RE: Corrosion? happening on galvanized steel

It was a corrosion test? So can we sugest that the one sprayed with Sodium hypochlorite, was the most corroded !?


RE: Corrosion? happening on galvanized steel

Those chemicals sound like homebrew mold abatement.

RE: Corrosion? happening on galvanized steel

Yes. Mold remediation was conducted by spraying a mold remover solution(ingredient: Sodium hypochlorite, Sodium carbonate, Sodium hydroxide) on almost the whole house during framing one year ago. So almost all connector plates were also sprayed by that chemical.
That chemical has been left on the surface on the steel plates since then. Now, most of the connector plates in the attic are like these pictures.
The attic could be humid in some circumstances and it could get a water leak during a storm. Some condensation on the roofing nails in winter has already been observed.
Will the steel part of these plates get corroded fast in this environment since Zinc is already sacrificed?
If so, how soon may it happen from your experience?

RE: Corrosion? happening on galvanized steel

Once thr zinc layer is gone, corrosion rate would possibly slow down. However, the steel would start to look ugly.
Apply a coat of epoxy zinc paint to enhance the steel life.

Kolkata, India

RE: Corrosion? happening on galvanized steel

Do you know how long it takes to develop from Zinc corrosion(white rust) to steel corrosion(brown rust) typically?

Almost all truss connector plates of this one-year old house look like these pictures.
Is a repair required immediately to extend the longevity of the structure?
How to repair? With WD40?

RE: Corrosion? happening on galvanized steel

Are you near the seacoast?
Or someplace very hot and humid?
If not then don't worry about it.
Even if the plates rust it will just look ugly. They will still work fine.
Near the sea, then I might think about giving them a brushing with a wire brush.
Just by hand to knock off any loose material.
Then painting with a Zn rich paint.
You could use a small roller.
I wouldn't worry about it though.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

RE: Corrosion? happening on galvanized steel

Coat with Fluid Film if you're old-school or thixotropic gelled calcium sulfonate if you're new-school.

No need to brush with either coating.

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