How Long Does It Take For Galvanized Steel To Rust

How long does galvanized steel last?

So how long does it take for a handy galvanized steel bucket to rust and corrode into a useless pile of metal? It takes a long time. A galvanized steel bucket (made by any method) can practically last forever if it is used gently and kept dry and out of the rain. But for galvanized buckets and tubs intended to be garden pots, landscape decorations, fodder containers and farm water buckets, corrosion is inevitable. Galvanized steel for extended outdoor use shall be hot-dip galvanized steel; typically lasts about 70 years in a variety of environments. Table 1 below predicts the service life of galvanized steel based on a 30-month corrosion study of environmental factors such as humidity, humidity and air pollutants in 2004. Table 1. Projection Prediction of when the zinc layer will be consumed on galvanized steel Galvanized steel is kept in a humid environment or immersed in water 10 Years with 100% relative humidity 34 Years with less than 60% relative humidity. 211 years Source: Construction Materials Journal 2004 (11) The corrosion resistance of zinc coatings is determined primarily by the type and thickness of the coating but varies with the severity of the environmental conditions contact (as shown in the table above). The corrosion resistance of hot-dip galvanizing depends mainly on a protective film (rust layer) formed on its surface. Read more background information: Read: how long does galvanized steel rust

Plating types; Comparative properties of galvanizing methods.
Does galvanized zinc rust; Learn how hot-dip galvanizing corrodes to form a layer of rust that can protect the underlying zinc metal for up to 75 years. The zinc corrosion products of hot-dip galvanizing accumulate (creating rust) and adhere to insoluble metals in many environments. Therefore, the corrosion rate of hot-dip galvanized steel can slow down over time.

The type of galvanizing and how that process controls how the galvanized steel corrodes must be understood in advance. However, the environments, factors, and conditions that any given galvanized steel is exposed to, really determine how long it will last before it corrodes. A 1926 study of galvanized steel corrosion in industrial, rural and marine areas found:

At any given location, the life of the galvanized coating is directly proportional to its thickness.
Corrosion is fastest occurring in highly industrialized locations, and least rapidly in more rural and arid areas (9).

Read more: How to use a USB webcam on a chromebook The handy chart below (from the American Galvanizing Association) illustrates how long galvanized steel will last before corroded areas should be serviced to prevent further damage. Want to learn how to finish galvanized steel? Click here. In other words, this chart shows how long it takes for galvanized steel to rust in different environments. The thicker the zinc coating, the longer the galvanized steel will last without corroding. The thickness of zinc is shown along the horizontal axis (8). As shown in the chart below and documented in the 1926 study, for each site the corrosion rate is essentially constant over time (9). Figure 1: Time of first signs of corrosion in different environments The environments below are listed from most corrosive to least corrosive: Industrial environment:

Most city and urban areas are examples of urban environments.
In general, the most corrosive medium.
Sulfur and phosphate air pollution, from point sources such as automobile exhaust, causes the consumption of galvanized zinc coatings.

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Tropical marine environment

Areas where temperatures drop below freezing.
Humidity is high and chlorides from nearby water are present in the air.
Corrosive almost industrial environment
Warm temperatures increase the activity of corrosive elements on the surface of galvanized zinc.
Location near the coast, wind direction and wind speed also affect the rate of corrosion

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Lower temperatures and humidity make temperate marine environments less corrosive than their tropical counterparts.
Like tropical seas, chloride, distance from the ocean, wind direction, and wind speed shape the rate of corrosion.

Suburban environment

Less susceptible to corrosion than industrial sites
The peri-urban communities outside urban areas and cities.

Rural environment

The strongest corrosive atmosphere
Air and rain in rural areas contain relatively low levels of sulfur and other corrosive emissions.

Factors and conditions: Air Sulfur Dioxide (SO2) is the most significant air pollutant. The presence of SO2 in the atmosphere largely regulates the rate of atmospheric corrosion of zinc. When acid – with a pH below seven – attacks and corrodes the zinc coating, the pH decreases and the rate of corrosion increases. In industrial sites, mists and mists have been observed to have a pH as low as 3. Therefore, it is reasonable to attribute the more corrosive industrial atmosphere to SO2 gas pollution. acids contained within them (9). The results of a corrosion study on galvanized metal published in 2015 showed the highest corrosive effects from SO2, dust, moisture and CO2. Concentrations of these pollutants are highest in winter; as fossil fuel combustion increases. The presence of chloride in the air also affects the rate of corrosion (10). Soil Just as the acidity of the atmosphere affects the rate of corrosion, so does the acidity of the soil. The galvanizing layer of hot-dip galvanized steel will last in the harshest soils for 35 to 50 years and in less corrosive soils for 75 years or more. Temperature Although humidity affects corrosion, temperature itself has less of an impact. The zinc plated finish responds well to extreme hot and cold temperatures. There is no significant difference in corrosion rates at temperatures below -40 F for hot-dip galvanized coatings. At higher temperatures, zinc can be subject to impact. For continuous long-term exposure, the maximum recommended temperature is 392 F, according to a statement from American Galvanizers (8). Such high temperatures can cause the outer zinc layer to peel off the zinc alloy layers. Although the remaining zinc alloy layers will protect the steel against corrosion, the protection will last for a shorter time than if the outer free zinc layer had remained intact. Because steel’s applications are so numerous, hot-dip galvanizing will continue to be required to ensure long-lasting and maintenance-free corrosion protection.