Stainless steel has a natural silver luster and resistance to corrosion. These qualities are what usually recommend the alloy compared to regular steel. For most customers it makes very little sense to cover the stainless in a powder coat or other finish. However, customers occasionally choose a colorful finish on stainless, and we thought to walk through the pros and cons.
Why choose powder coating on stainless steel?
Stainless steel can be finished with paint, powder coat, or IronArmor.
Color is one common motivation for coating stainless steel. The natural finish on stainless steel fits many sites, but not all. Some places choose to choose complementary or coordinating colors for their site furnishings. Designers may choose powder-coated stainless steel when that’s the only way to choose their preferred shape or bollard weight.
Many stainless bollard covers fit this profile. Lightweight and sleek, with flat and wedge tops available, these covers are chosen for both their modern form and the ease at which a single worker can install them.
For other bollards bollards, stainless with powder coating together create superior corrosion protection. A coating doubly protects against oxidizing elements. For extra-long-lasting protection, stainless and a color finish are an excellent choice.
Common applications for powder-coated stainless
Stainless steel is famously corrosion resistant—but it is not corrosion proof. Some chemicals can challenge it. Iron deposits, chlorine, and salt can all challenge stainless alloys (with some being more resistant than others.)
De-icing chemicals in wintery locations can become a challenge. Chlorinated water is also very oxidizing. Most interesting is the destruction even a light scrape of iron or steel can start. Ferrous elements throw off the surface chemistry of stainless. When these factors are present, a coating can work along with the stainless steel’s natural abilities, and increase the longevity and attractiveness of the item. Water parks, marine environments, and workshops are common places to see powder coated stainless. Railings are also often powder coated stainless, for corrosion resistance without the same propensity to pick up fingerprints. This is especially true if they’ll be bumped by items containing steel. Places where carts, bikes, barbeques, or skateboards might rub against the rail may choose to powder-coat on stainless.
Our stainless steel retractable bollards can be finished with powder coat or IronArmor. These bollards slide and are stored in below-ground receptacles. Extra peace of mind may come with a protective coat in wet or salty conditions.
Choosing finished stainless
If choosing stainless for color or weight, first check and see if there is an equivalent product in powder-coated steel. Similar shape and comparable weight items may be available in another alloy. Bike rack designs, for example, come in both unfinished stainless and finished steel. It is less expensive to produce quality steel than to produce quality stainless. Steel is also easier to finish. Therefore, changing the material may offer a cost savings, with no drawback.
However, stainless steel can be an excellent base alloy for additional corrosion resistance, especially in places where there is a lot of chlorine. Some products may also only be manufactured in stainless like our retractable bollards. Color finishes like paint, powder, or IronArmor double up with a passivated stainless to prevent oxidization and corrosion of the metal.
How to powder coat stainless steel
To have powder coat or IronArmor adhere to stainless steel, care must be taken to create excellent adhesion. Stainless steel is “stainless” because of its chemistry. It always has chromium, and depending on the specific alloy may also have nickel, molybdenum, or other elements. The complex chemistry of this alloy group means that some standard processes, like phosphate pretreatment, are not as effective and can lead to poor adhesion.
Even still, powder-coated stainless is common. Manufacturers create great adhesion during the process all the time. Depending on the type of part and alloy, these steps are common:
- Pickling and/or passivating
- Primer and powder topcoat
Oil and dirt can interfere with subsequent steps, and so a surface clean is usually done on smudged materials to remove them.
Pickling and/or passivating
This is not your grandmother’s pickle recipe! Metal pickling liquor uses heavy acids to strip metal surfaces, removing a thin layer. It has to be done carefully to prevent pickling from causing corrosion. This step may be important for welded pieces that have less chromium near weld points. Some alloys may be pickled, passivated, and pretreated: three chemical processes to prepare for powder-coating. However, stainless finishes often get physically treated to create excellent finish adhesion.
Blasting (and cleaning part two)
Blasting is a common pretreatment with stainless, usually more precisely controllable than acid pretreatment. Once the part is well sanded, it is cleaned again so no fragments or blasting agent remains.
Primer and powder topcoat
Powder coating and IronArmor are both finishes applied in thin, even layers using electrostatic charge. This process ensures complete coverage, without pinholes as might appear in paint. A successful powder-coat starts with an excellent primer.
Powder coated parts are oven cured until the resins harden, for scratch- and abrasion-resistant finished surfaces.
Choosing metal and color
The right outdoor metal product for an application should be chosen for style, value, function, and compatibility with local conditions. Heavy ductile iron and steel are often chosen for their traditional weight and structure. Aluminum is light and does not rust the way ferrous metals do. Stainless offers steel’s material profile with aluminum’s corrosion resistance. Choosing to powder-coat stainless is an excellent option for specific applications, when strength, corrosion-resistance, and style all come together to recommend it.