huangyhg

preventing further steel corrosion
hi guys,
i am currently doing some renovation work where i am checking the structural adequacy of an suspended walkway that has undergone some corrsion.
what measures can i take to ensure that any further corrsion is minimised in the future.

sandblast and paint with anti-corrosive paint
is this a steel or reinforced concrete walkway?
steel, all remedial measures that can take place need to happen on site. is grit-blasting to expose the 'shiny' metal a expensive and messing solution.
the corrosion is particularly severe in places, the base plate was initially 10mm thick (3/8") and has corroded down to 6mm (2/8").
grit blasting to 'white metal' can be relatively expensive (compared with other solutions) and it is messy, but it is also the best if you want to ensure proper painting and corrosion protection
you could try wheelabrading with mechanical wire brush followed by a 'surface tolerant' primer. those primers tolerate steel surface in less than ideal conditions.
but if you say that the plate has corroded so much, that means that the environment is not ideal. so the better a job you can do, the more corrosion protection you will get.
in any case, independently of what you decide, it is also very important to carry out regular, proper maintenance on the walkway, reparing and touching up any future paint damage or degradation. that, in my opinion, is critical.
also, what is the root cause of the corrosion? is there exposure to de-icing chemicals? how is the drainage? are the corroded areas exposed to enough ventilation to dry out after getting wet?
properly applied coatings are great, but reducing the moisture makes them more efficient.
if you have lost 40% of the steel - it might be time to replace it. by the time you get done sand blasting or grinding - you will probably be down to 50% remaining - not usually a good thing....
abrasive blast to sspc-6 (near white). sspc-6 requires degreasing with solvents prior to blasting.
apply zinc rich primer, apply intermediate epoxy stripe coate to all sharp corners by brush. apply epoxy intermediate coat. apply polyurethane top coat. paint manufacturer's will be glad to give you a standard coating system and required dry film thicknesses.
pay attention to any reactive metals. is say stainless steel grating on carbon steel members? this could promote corrrosion of the carbon steel.
visit the nace website for further information on standards etc. (national association of corrosion engineers).

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