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Lifespan of galvanized sheet metal?

Q. I have an existing concrete seawall. It is crumbling. I want to put galvanized corrugated metal against it against the lake. As it is galvanized, how long will it last before it starts to rust?

david weiss

- cassopolis michigan

Hi David,

It can be often measured in decades. It depends on a number of factors, though, primarily thickness of the galvanize and the environment it is exposed to (including temperature & salinity but not limited to them).

See if your supplier/installer can give you examples of similar projects they have worked on which have been out in the world for a good number of years.

Useful reading:
galvanizeit.org/hot-dip-galvanizing/how-long-does-hdg-last/in-water

Jenna Tong

- Melbourne, Australia

Closely related Q&A's, oldest first:

Q. Hello,

I have to cover the styrofoam on the base on my new home (the styrofoam covers the cement foundation that has been back-filled) and I have chosen 7/8 corrugated metal - galvanized (Z275). I was not going to use a drip edge at the bottom, but rather, have the galvanized sheets go into the ground (crushed rock) for the most part and then use a drip-edge around the entry-points where there is a cement slab. The material is 26 gauge sheets of corrugated metal and I am running it vertically on the base of the house. The most that the metal will be into the ground is about 2 or 3 inches.

The company that I have purchased this from has stated that it will not be a problem and because the sheets won't be in standing water, they should not rust for a long period of time. So I'm not sure if this means the corrugated metal will rust in 20 years as opposed to 40 or fewer...any thoughts or further comments would be greatly appreciated!

Dennis Marchiori

installer - Yellowknife, NT, Canada

A. Dear Dennis,

The corrosion rate of a zinc coating varies widely depending upon many environmental factors. For
example, "time of wetness" is an important issue that affects corrosion rate, i.e., outdoor applications in
the dry Southwest United States are very different from locations that experience high annual rainfall or
extended foggy periods. Also, the presence of impurities such as sulphates, chlorides, and nitrates can
dramatically affect the rate of corrosion. Other variables, including the amount of oxygen present in the
electrolyte, and the temperature of the environment are important determinants for predicting product life

It means that within 3 - 15 years you could have a problem if you use it totally underground, if we may believe the website of "canada culvert", but before you explode, please read everything, as it is a bit more complicated as you may think:
GALVANIZED Z275 coating is a light, 275 g/m2 commercial galvanized coating suitable for short-term projects (three to 15 years). Where generally standard galvanized coating (610 g/m2) corrugated steel pipe provides a life of 45 years or more, a suitable alternative when such a life span isn't required is coating Z 275. Galvanized Z 275 is a zinc coating for short-term corrosion protection in temporary applications where culverts will be abandoned such as forest applications. Z 275 offers a substantial savings because it reduces the zinc coating by more than half and ultimately reduces the risk of zinc leaching into the surrounding soil and water. CANADA CULVERT's Z 275 coating is ideal for forestry roads that will be deactivated, temporary lease roads, construction site drainage, or temporary cribbing applications.

But as they say, this is applicable for zinc plated steel tubes, used in the ground, drenched in liquids

If the steel is only used in a dry, non polluted area ... it will last long. If it is in contact with moisture and in contact to the rain, air, ground etc. you could encounter problems. The type your supplier supposes is commonly used in architectural applications, also outdoors. In general it will last 40 years in a rural area and approx. 25 years in an industrial area. If you want to be sure that you always have 50 years lifetime in a industrial area, you should change your choice, In that case you should talk a bit more to your supplier and ask for the thicker galvanized qualities... or construct it in such a way that you can easily replace it if the worst comes to the worst.

If you want to become an expert, start here:
http://www.galvinfo.com/galv_info_notes.htm
(and start with note nr.1.6.)

Best regards and lots of success,

Harry.

Harry van der Zanden

- Budapest, Hungary

  Hello Harry,

Thanks for that information and for the forwarding links, that does help me out. As the climate up in northern Canada is fairly dry (rains a bit in the fall), but mainly snow and frozen with an extended fall, then the z275 coating will work well for me.

Plus, as you've noted, if they are saying 3 to 15 years for a pipe completely underground and containing liquids, I should be alright (and I've done it so I can easily remove or replace sections).

Thanks again.

Dennis Marchiori

[returning]

- Yellowknife, NT, Canada

Q. Hi , I live in London and want to create a raised bed for my plants using galvanised corrugated steel as the front retaining wall . The back of the bed would be made from scaffolding timber or something like it . I want to use corrugated steel about 2.5 ft high , held in place with 2x2 posts, to get a nice wavy or curvy undulating line along a very linear L - shaped garden and thought this would soften the rigid and sharp angles .
Would somebody please advise me as to whether this is practical solution to get the effect I want or whether this is a stupid idea using an impractical material for the purpose. It looks great in my head and if you can give me some practical advice I'd be so grateful. Thanks for reading .

Marcus Naidoo

Amateur Gardener - London, England

A. Hi Marcus. The general theme sounds okay but 2 x 2 wood posts are not going to be able sustain a load which is sufficient to bend the corrugated metal. Maybe 2 x 2 steel angle irons embedded in concrete on 6' centers or so :-)

Luck & Regards,

Ted Mooney

, P.E. RET

Striving to live Aloha

finishing.com - Pine Beach, New Jersey