huangyhg

paint as good as hot dip galvanize
is there a paint as good as hot dipped galvanizing out there ? i have some existing painted steel which is at present inside that will be exposed to the outside atmosphere and must be painted to a standard as good as hot dipped galvanize.
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in my opinion, no. applied high performance coating systems can provide excellent protection, with surface preparation the most important step, but hot dipped galvanizing is the premier coating.
the main difference is durability, properly specified galvanising will last a lifetime, paint needs to be redone every 10 or 15 years.
try a zinc rich paint, these straddle the line between the two.
or you could ude a belt and suspenders solution and paint hot dip galvanized steel.
jed,
i think the op was mentioning that the steel was existing already in place. also, that seems like an idea that came from the department of redundancy department.

rc
all that is necessary for the triumph of evil is that good men do nothing.
edmund burke

jed, there are actually a lot of issues with painting over galvanising due to the pickling residue
civeng80
to answer your specific question (as i interpret it), yes you can find a paint system which will give similar protection as galvanising, if it is not possible hdg the existing items you have.
if you can hdg it then do that, as it will be more robust and probably cheaper.
if you can't hdg because the part is in place, you can use use thermal-spray metallizing.
a properly applied zinc-rich paint system can last a good long time. best is inorganic zinc with no topcoat, if you don't care about color--there are test panels out there that have been up for decades and are doing fine. you need to make sure that the surface is cleaned to bright metal before you apply the paint.
hg
zrc makes a cold galvinizing compound. is it as good as hot dipped? probably not. iss it suffucient for your purposes? probably. and is that not the right question to ask?
civeng80,
i think you have the sense of comments here that no paint system is actually as good as hdg, which was your question. but if you have to provide a durable paint system to an existing structure, the most important thing is the preparation. as the existing steel is interior, it probably has only been painted with an architectural coating not designed for exposure. to get a durable coating, the existing coating would have to be removed. i would consult with one of the industrial coatings manufacturers for a suitable system. it will likely involve an epoxy zinc rich primer (not inorganic zinc, which is only for shop work), and top coats to complete the system.
epoxy paint systems can be the equal of galvanized with sufficient thickness.

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