Why does galvanizing protect iron from rusting

Most other corrosion protection coatings will degrade on exposure to solar radiation. This is usually one of the key limiting factors to the performance of such coatings. The problem with conventional barrier protection, such as painting, is that it will not prevent corrosion if the base steel is exposed due to mechanical impact damage or abrasion. In fact, some barrier protection can allow corrosion to proceed undetected in the form of under film corrosion. In the event of severe mechanical damage and exposure of the base steel to the environment, galvanizing also provides cathodic protection.

The galvanizing performs in a similar way to other sacrificial protection systems, except in this case the sacrificial anode is distributed over the article to be protected and electrical continuity is assured. The cathodic protection characteristics of galvanizing ensure that mechanical damage does not result in concealed under-film corrosion and potential catastrophic failure prevalent in some other protective coatings.

Where continuity of the galvanized coating is broken by cut edges, drilled holes or surface damage, small areas of exposed steel are protected from corrosion cathodically by the surrounding coating. No touch up is necessary, and cathodic or sacrificial protection continues for many years. In service, zinc corrosion product tends to build up in coating discontinuities, slowing the rate at which the surrounding coating is consumed in protecting a damaged area.

A common practical example of this cathodic protection phenomenon is the uncoated internal threads of certain fasteners. The uncoated internal threads of galvanized nuts are protected from corrosion by the zinc coating on mating bolts and studs. When substantial coating damage has occurred to a galvanized coating during handling, fabrication or erection, coating repairs are necessary. In the presence of an electrolyte, the anodic zinc coating of a galvanized article corrodes preferentially to the cathodic steel base, preventing corrosion of small areas which may be exposed.

The cathodic or sacrificial protection continues for as long as some of the galvanized coating remains. This stops oxygen and water reaching the metal underneath - but the zinc also acts as a sacrificial metal.

Zinc is more reactive than iron, so it oxidises in preference to the iron object. A reactivity series lists metals in order of how reactive they are. Is stainless steel or galvanized more rust resistant? The addition of chromium as an alloy helps to protect against rust and corrosion. Galvanized steel, on the other hand, is a type of steel that has been coated in a layer of zinc. Which is better Galvalume or galvanized? Galvalume is offered in both bare and pre-coated versions.

How do you rust proof steel? If rust forms on the steel, there are ways to rust-proof it again. Scrub off any rust on the steel with a scrubbing pad or wire brush.

Apply a rust-proof or rust-inhibiting primer to the steel with a paintbrush. Allow the primer to dry completely. Re-apply the primer periodically to keep rust at bay. What is better zinc plated or galvanized? The big difference is thickness: zinc plating is normally 0. Hot dip galvanizing might be 1. The galvanized product will develop a white protective coating zinc oxide that adds to its protective properties.

What is the best metal for salt water? While aluminium is light, it has limited corrosion resistance in seawater and requires significant maintenance. Stainless steel, on the other hand, is recognised as the premium material for marine applications where it is used for its excellent corrosion resistance, lustre, strength and stiffness.

Rust is an iron oxide typically a red oxide which is formed by the reduction and oxidation reaction of iron and oxygen, in the presence of water or air moisture. There are protective methods such as painting or plastic coating, but these methods do have drawbacks. When damaged, sections of the steel will become rusty and the protective coating will fall away, making these types of protection non-lasting and unreliable always needing continued maintenance.

One of the better methods of protecting steel materials against corrosion is through hot-dip galvanization.

With hot-dip galvanization, all the surfaces of the material are dipped into, and completely coated with, molten zinc. The corrosion of zinc is very slow, which gives it an extended life while it protects the base metal.

Due to the alloying of the Zinc to the iron, cathodic protection occurs. This ensures that small areas of steel which may be exposed through damage are not compromised by rust.