Zinc Phosphating
We can meet your stringent standards for uniform conversion coatings that help your finishing paints, oils, and lubricants adhere to parts.
Enhance the Surface Qualities of Your Metal Parts
Zinc phosphate coating protects against corrosion, reduces electrical conductivity, promotes adhesion, and improves the appearance of your parts.
What is Zinc Phosphating?
Phosphating transforms the metal surface of a component into a non-metallic, polycrystalline coating that contains iron, manganese, nickel, and zinc phosphates. It has several benefits and is commonly performed on parts that will later undergo painting or other surface treatments for finishing. This coating provides high alkaline resistance and is preferred as a paint base offering superior adhesion and durability.
Benefits of Zinc Phosphating
- Fighting Corrosion
Rust is the first thing that springs to mind — everybody knows how hard winter road salt is on a car’s body — but that’s not the only challenge metal industrial parts face. Any metal part that’s exposed to corrosive chemicals should have a protective coating.
Phosphating is one of the most popular ways to provide that protection because it’s much safer for the environment than older coatings that relied on lead and other toxic substances. - Reducing Conductivity
Every metal conducts electricity — which is beneficial for transmission cables and wires within electrical devices. The trouble is that many of these devices use metallic screws, cases and other components.
These metal components need to be non-conductive. Otherwise, they’ll reroute electrical current away from wherever it’s supposed to go and provide an annoying electric shock to anybody who touches the metal. Phosphate coating reduces the conductivity of metal components to prevent this from happening. - Promoting Adhesion
Think about what happens when you splash water on your bathroom mirror in the morning: the droplets just slide right down the surface of the glass. Many metal surfaces are slippery in the same way, but they need a coat of paint that will stay in place for years of use. Other metal parts need to be lubricated, but the lubricant, being slick, slides right off.
Zinc phosphating adds a slightly rough layer to the exterior of a piece of metal that gives paint, rust-inhibiting oils, and lubricants something to grab onto. It is also commonly done prior to powder coating to yield a consistent application and appearance. - Improving Appearance
Most bare metals aren’t much to look at (unless you’re really into gray), and their coloration is inconsistent over the entire surface of a part. This process provides a consistent color and tone that makes metal parts more aesthetically appealing.
Lots of today’s high-tech consumer products have metal surfaces held together with machine screws that help create a space-age look and feel. Zinc phosphating is one of the processes which enable that kind of visual appeal.
Paulo’s Approach to Zinc Phosphating
We understand the importance of consistency when it comes to your metal finishing processes. That’s why our zinc phosphating lines are computer-controlled to ensure quality, repeatable processing that meets your specifications.
Our treatment process uses a drum three feet wide and two feet in diameter. It’s best for a large volume of small parts like screws, nuts and bolts that will tumble together while they’re being treated. It’s not ideal for big parts like automotive structural components.
Our automated processes mean we can handle large lot sizes in quick time frames. And because we can process for multiple user needs, we can do things like add post coatings with oils and sealants to boost corrosion fighting or add lubricity.
And of course, all of our phosphating processes comply with industry and quality standards.
Zinc Phosphating FAQs
Can you paint directly over zinc phosphate coating?
Yes, that’s one of its primary benefits. Zinc phosphate creates an ideal surface for paint adhesion. The crystalline structure of the coating gives paint something to mechanically grip, and the chemical properties of the phosphate layer promote good bonding. Many automotive components are phosphated specifically to prepare them for painting in subsequent operations.
Does zinc phosphating create hydrogen embrittlement concerns?
Like zinc plating, phosphating does involve chemical processes that can introduce hydrogen into parts. For hardened parts (particularly those above HRC 32), there is some hydrogen embrittlement risk. We can perform hydrogen embrittlement relief baking if required, following the same protocols we use for zinc plated parts. However, we don’t guarantee 100% elimination of hydrogen embrittlement—this is a limitation of the process across the entire industry, not unique to Paulo.
Does zinc phosphating provide corrosion resistance?
Yes, zinc phosphating provides some corrosion resistance, primarily because the porous phosphate coating holds oil very well. That oil layer is what actually provides most of the corrosion protection. The phosphate coating by itself offers modest corrosion resistance, but when combined with oil (which we apply as part of the process), it becomes quite effective at preventing rust, especially for parts that will eventually be painted or are stored temporarily between manufacturing operations.
What is zinc phosphating?
Zinc phosphating is a chemical conversion coating that creates a dark, non-metallic crystalline layer on steel surfaces. Unlike zinc plating (which deposits metallic zinc), phosphating chemically converts the steel surface itself into zinc phosphate crystals. The resulting coating is typically dark gray to black in appearance and provides a base for paint adhesion, holds oil well for corrosion protection, and gives parts an attractive matte black finish.
What size and type of parts can you zinc phosphate?
Like our zinc plating, we phosphate parts in barrels, which works best for small parts—fasteners, clips, brackets, and similar hardware that can fit in the palm of your hand.Â
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