As much as oil and water will not mix, so does two individual coatings of oil. This is the problem when you try to paint galvanized steel without subjecting it to appropriate treatments beforehand. Do not let yourself struggle in making it happen, it’s never going to happen. Before we try and figure out how to make ends meet, let us first start on trying to understand what makes up galvanized steel and paint to further understand why the two just won’t be friends.
Components of Galvanized Steel
Steel, in its most basic form, is a mixture of iron and carbon along with other elements that help it to become a strong alloy. For stainless steel, which is very costly, it needs to have around 11% chromium to make it corrosion and oxidation resistant. But we are not up for that, we want ourselves galvanized steel.
To form galvanized steel, a zinc coating is applied to the carbon-iron alloy, furthering in preventing white or brown rust. The most common process in doing so would be hot-dip galvanizing, wherein the steel would be dipped in molten zinc for it to get covered much like a piece of chicken being breaded before frying.
Another method used is electro galvanizing, making use of ions in the metal and maximizing their potential to add a thin layer of zinc to a given metal. This is usually done for steel that is to be treated with decorative coating after galvanizing.
Lastly, there’s thermal fusion galvanizing or sherardizing that it makes use of a zinc diffusion coating. This is to be applied to a preferred metal made of steel or iron through a sealed rotating drum. You proceed by tumbling the metal and the zinc powder together at around 300 degrees Celsius, forming a zinc alloy by the end of the process.
A common feature of galvanized steel is the very visible spangle on its surface which are crystallites formed through heterogeneous nucleation upon undergoing the hot-dip process. The size of the crystals, of course, can be controlled; being able to have grains that are centimeters wide or even crystallites too small to be distinguished by the naked eye.
Components of Paint (Alkyd or oil-based)
Paint usually has three components: the binder, the pigment, and the thinner. When the paint is oil-based, it is known to have a binder be either made from linseed (a natural oil) or alkyd (a synthetic oil). Of course, the synthetic-based oil is comparatively cheaper but is known to work a lot stronger. Although, both types of oil-based paints are known to be durable and tough and can withstand a lot of wear and tear. That is why it is commonly used for painting the exterior of the house, the bathrooms, the kitchen cabinets, the trims, or even doors.
So why doesn’t it mix?
When using oil-based paints on galvanized steel, the paint would adhere for a good while until it quickly gives, fails, and peels off. This is due to both materials undergo saponification, in which a soapy film is formed upon the reaction of the alkyd binder of the paint with the coating of zinc that protects the galvanized steel from rust and corrosion.
How to make the painting happen
To make sure that you get the most optimum results when painting over galvanized steel, here is what you have to gather:
- 240 grit heavy-duty sandpaper
- Tack cloths
- Metal primer
- Metal paint with the same brand as the primer (make sure it works for galvanized metal)
Now you have everything you need, here are the instructions on how to proceed with painting:
- Wash the metal using soapy water that is relatively hot
- Rinse the metal accordingly and let it dry for a couple of hours
- Create a weak ammonia-water solution. Rinse the metal with the solution and let it dry for a couple of hours again
- Remove attachments or handles in the metal that may become an obtrusion when sanding
- Thoroughly sand the entire surface area of the metal with the 240-grit sandpaper, making sure to get dents and crevices on the metal
- Wipe the sanded surface with tack cloth when finished
- Apply the metal primer as directed in its canister. Make sure you cover the entire surface area of the object, working by sections from top to bottom
- If drips are starting to manifest, wipe it as soon as possible
- Let the primer dry as insisted by the instructions in the canister
- When dry, inspect the object if its surface is perfectly covered by the primer you just applied
- Read through the instructions of the metal paint written on its canister
- With that knowledge in mind, start applying the metal paint taking note of the considerations given in the canister’s instructions
- Let the paint dry as insisted by the instructions in the paint’s canister
- Again, inspect the layer of paint you have just put on across the surface of the object once it is fully dried
Union Galvasteel’s Prepainted products
If you want to skip out on all the hassle, us here at Union Galvasteel Corporation (UGC) offer roofing materials that are already painted for your convenience. Being one of the Philippines’ top roofing manufacturer and contractor, you are sure that we only deliver quality that is sure to last you a very long time. Get only the lowest roof prices in the Philippines with Union Galvasteel Corporation.
For more information on the products and services of Union Galvasteel Corporation, you may call our Calamba office at tel. nos. (02) 8520-8823; 8520-8831 Trunk line or (049) 545-0084 to 86 Trunk line or click here.