May 28, 2020 by Universal Galvanizing
Maintaining a like-new finish on galvanized steel requires attention to two sets of activities. The first is preventing build-up on galvanized steel, and the second is removing build-up without damaging the zinc coating or the steel beneath it.
Preventing Build-Up on Galvanized Steel
The most important step in preventing corrosion on galvanized steel is keeping it out of environments where it is exposed to substances with a pH below 6 or above 12.
One side of this requirement is that it is important to keep galvanized steel out of acid rain. Ordinary rain has a pH of 5 to 6, which damaging if the steel cannot dry out. But acid rain often has a pH of 4 and can have a pH as low as 2. Washing galvanized steel with potable water that has a neutral pH is essential to preventing acid rain damage.
Exposure to pH over 12 can occur when galvanized steel is exposed to bleach or disinfectant. If a galvanized steel surface is disinfected, it must be washed with neutral, potable water as soon as possible after the disinfectant has had a chance to do its work.
Another long-term consideration in maintaining the finish on galvanized steel is insulating it from contact with dissimilar metals. Copper and brass encourage electrochemical reactions that deplete the zinc coating on galvanized steel.
Do not clean or degrease galvanized steel with abrasive cleansers. The process of wetting and drying in normal weather builds up a protective patina of zinc over galvanized steel that protects it from the elements. Constant abrasive cleaning destroys the patina, so it has to be built up over and over again, bringing time to first maintenance unnaturally early in the life of the steel.
When galvanized steel is placed in service in coastal or industrial locations, it needs to be washed with water on a regular basis to remove potentially corrosive salts and chemicals. And galvanized steel should never be stored in a damp, poorly ventilated warehouse.
Removing Build-Up on Galvanized Steel
With responsible maintenance programs, galvanized steel will accumulate minimal build-up once it is in service. But it is not uncommon for contractors to be unaware of or insensitive to the need to store newly galvanized steel in pristine conditions so that stains and marks occur before the steel is placed in service.
Fortunately, there are a number of options for removing stains and marks on galvanized steel. But there are some general rules for successful removal of build-up on galvanized steel.
- Always opt for the most conservative approach to cleaning steel. If relatively gentle methods don’t work, then move up to more vigorous cleaning methods.
- Avoid mechanical and abrasive cleansing methods whenever possible. Mechanical methods of cleaning zinc surfaces result in aesthetic issues. When scrubbing is required, use a hard plastic brush rather than a steel brush to minimize the visual contrast between areas needing cleaning and those that don’t.
- Test any cleaning method in an inconspicuous area first before applying it to the entire surface of the steel.
General contaminants like dirt are easily removed with laundry soap. The more stubborn areas may need a pressure wash after application of soap. Soaps used to wash cars and trucks are designed to protect metals and often get good results on galvanized steel.
Mild stains from ponding of water and beverage (particularly wine and soft drink) stains usually respond to application of household ammonia cleaners. Dilute the ammonia cleaner to avoid excessively high pH that can damage zinc, and rinse off the ammonia cleaner with potable water after it removes the stain.
Brown stains from runoff from adjacent untreated steel can be removed with the same oxalic acid cleaners used to clean pots and pans. Oxalic acid also helps to remove cement and mortar.
Graffiti should be removed with a combination of non-alkaline paint thinners and wooden or plastic — never metal — paint thinners. Rinsing after paint removal is important so potentially corrosive chemicals are not left on the galvanized surface.
Looking for a place to get started with stain and build-up removal?
The American Galvanizers Association (AGA) has tested some widely available commercial products for removing organic contamination with good results. These products include:
- Comet®
- Bleach
- Goof Off®
- Simple Green®
- The Must for Rust®
- Stainless Steel Cleaner
The AGA recommends these products for removing stains:
- CLR
- Lime juice
- Naval jelly rust dissolver
- Picklex 10G
- White Vinegar
Always test vinegar, ammonia cleaners, and muriatic acid in inconspicuous locations before applying over large surfaces.
I'm an expert in the maintenance of galvanized steel, and I'll provide detailed insights into the concepts mentioned in the article dated May 28, 2020, by Universal Galvanizing. The information is crucial for maintaining a like-new finish on galvanized steel, focusing on preventing and removing build-up without causing damage to the zinc coating or the steel beneath it.
Preventing Build-Up on Galvanized Steel:
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Environmental Exposure: Galvanized steel should be kept away from environments with a pH below 6 or above 12. Acid rain, with a pH as low as 2, can be particularly damaging. Regular rain, with a pH of 5 to 6, can also be harmful if the steel cannot dry out.
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Washing with Neutral Water: Washing galvanized steel with potable water that has a neutral pH is essential to prevent acid rain damage. This is crucial after exposure to substances like bleach or disinfectant, which can raise the pH.
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Avoiding Contact with Dissimilar Metals: Long-term maintenance involves insulating galvanized steel from contact with dissimilar metals such as copper and brass, which can lead to electrochemical reactions depleting the zinc coating.
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Avoiding Abrasive Cleansers: Galvanized steel should not be cleaned or degreased with abrasive cleansers. The wetting and drying process in normal weather build up a protective patina of zinc that is destroyed by constant abrasive cleaning.
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Coastal and Industrial Locations: In coastal or industrial locations, regular washing with water is necessary to remove potentially corrosive salts and chemicals. Galvanized steel should not be stored in damp, poorly ventilated warehouses.
Removing Build-Up on Galvanized Steel:
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Responsible Maintenance: With responsible maintenance programs, galvanized steel will accumulate minimal build-up once in service.
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Storing Conditions: Newly galvanized steel should be stored in pristine conditions to avoid stains and marks before being placed in service.
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Cleaning Methods: Opt for the most conservative approach to cleaning steel. Mechanical and abrasive cleansing methods should be avoided whenever possible.
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Test Cleaning Methods: Test any cleaning method in an inconspicuous area before applying it to the entire surface. Always start with gentle methods and escalate if necessary.
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Contaminant Removal: General contaminants like dirt can be easily removed with laundry soap. Stubborn areas may require a pressure wash after soap application. Mild stains from water ponding and beverage stains can be treated with household ammonia cleaners.
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Stain Removal Products: Various commercial products have been tested for removing organic contamination and stains on galvanized steel. Some recommended products include Comet®, Bleach, Goof Off®, Simple Green®, The Must for Rust®, Stainless Steel Cleaner, CLR, Lime juice, Naval jelly rust dissolver, Picklex 10G, and White Vinegar.
Always test vinegar, ammonia cleaners, and muriatic acid in inconspicuous locations before applying them over large surfaces. This comprehensive approach ensures effective maintenance of galvanized steel with minimal risk of damage.
