In ZAM steel production, the Zn–Al–Mg coating provides high corrosion resistance, but the durability of the coating does not depend solely on the alloy composition . After the coating process, the surface still needs to be controlled and protected to limit reactions with the environment, maintain its appearance, and meet processing requirements.
That is why passivation for Zam steel has become an important step in modern Zam steel surface treatment systems.
What is ZAM roofing?
ZAM steel is a type of steel coated with a zinc-aluminum-magnesium (Zn-Al-Mg) alloy . The name ZAM comes from the chemical symbols of the three main components: Zn (Zinc), Al (Aluminum), and Mg (Magnesium) .
ZAM coatings contain approximately 6% aluminum and 3% magnesium , developed to enhance the protection and durability of the product. Thanks to its Zn–Al–Mg coating structure, ZAM steel sheets have superior corrosion resistance compared to some traditional coated steel systems such as galvanized steel and Galfan.
However, the inherent corrosion resistance of the plating does not mean that the ZAM surface is completely immune to environmental influences . During storage, transportation, processing, and use, the surface may be exposed to moisture, water, oxygen, fingerprints, or other agents.
Therefore, after plating, a solution is needed to stabilize and control the surface condition .
What is ZAM passivation?
Passivation for Zam steel is a chemical treatment process that forms a protective transformation layer on the surface of the plating , thereby limiting direct contact and interaction between the metal and the external environment.
To put it simply:
ZAM surface after plating → Passivation treatment → Formation of a protective film → Limits environmental impact
This film is very thin but plays a crucial role in controlling the reactions occurring on the metal surface.
For Zn–Al–Mg coatings, current passivation technologies can develop in several directions, most notably:
- Chrome III Passivation (Cr³ ⁺)
- Chrome-free passivation
In particular, Cr3+ systems can form films containing chromium phosphate compounds combined with organic silica components; while Cr-free technology can use silane and water-based resins to create a protective network on the surface.
Why should we passivate ZAM?
This is a crucial question for any ZAM sheet metal production line.
If the Zn–Al–Mg plating already offers good corrosion resistance, why is an additional chemical treatment step still necessary?
The answer lies in the stability of the surface after plating .
Enhances surface protection against environmental impacts.
Even highly corrosion-resistant coatings are still affected by moisture, oxygen, and environmental conditions during storage and use.
Passivation creates a transformation layer on the surface, which helps limit direct interaction between the plating layer and the environment , thereby helping to maintain the protective properties of the coating.
In other words, if the Zn–Al–Mg layer is the “main protective barrier” , then the Passivation layer can be seen as an additional surface control layer , helping the protection system to operate more stably.
Minimize unwanted surface variations.
One of the key requirements for commercially available ZAM steel sheets is not only corrosion resistance but also maintaining a stable surface appearance .
The surface after plating may continue to undergo chemical reactions when exposed to the environment. The passivation layer helps control these interactions, contributing to maintaining a more uniform surface condition during storage and transportation.
This is a particularly important factor for ZAM products that require high standards of appearance, cleanliness, and surface stability .
Reduce the risk of surface-related problems.
In actual production, a satisfactory ZAM surface is not judged solely by its corrosion resistance.
Manufacturers also need to consider:
Corrosion resistance → Appearance → Antifingerprint → Formability → Storage stability → Compatibility with subsequent coatings.
This is also the development trend of ZAM surface treatment chemicals: from solutions focused solely on passivation to multi-functional treatment systems .
Support for machining and surface quality requirements.
ZAM steel sheets are typically subjected to further processing steps such as forming, rolling, cutting, or surface treatment.
Therefore, post-plating treatment chemicals are increasingly designed not only to protect the surface but also to support requirements for friction, formability, and surface condition .
This is why next-generation passivation systems often incorporate TOC (Thin Organic Coating) functionality instead of simply creating a passive film.
Some common passivation chemicals for ZAM roofing
PrimeCoat® Z838 – Chrome III Passivator with TOC
PrimeCoat® Z838 is a phosphate/silane -based ZAM surface treatment solution , designed for multi-functional applications.
Depending on the process conditions and the amount of material to be processed, Z838 can be used in the following ways:
- Passive mode based on Chrome III.
- Water-based Cr3+ surface treatment.
- Fluoride-free.
- Meets RoHS requirements according to technical documentation .
Notably, PrimeCoat® Z838-4P is adjustable in terms of coating quantity. Depending on the application requirements, the product can function as a Chrome III passivation layer or create a thin organic TOC layer on the metal surface after plating.
As a result, the processing system can add features such as:
Anti-fingerprint – reduces friction – supports shaping.
A notable aspect of Z838 is its processing philosophy, which goes beyond simply “corrosion protection” and aims to simultaneously enhance the surface quality and machinability of ZAM steel.
View product details here ⇓
PrimeCoat® Z908 VH – Towards Chrome-Free Passive Technology
If the Z838 represents the Chrome III direction , then the PrimeCoat® Z908 VH takes the Non-Chrome direction .
Z908 VH is a water-based passivation chemical, developed using Phosphate/Silane technology , and is geared towards chrome-free passivation technology.
According to the provided documentation, Z908 VH:
- Does not contain Cr(VI).
- Does not contain other forms of chromium.
- Aiming to meet environmental requirements such as RoHS and REACH.
One notable point is that when applied at concentrations above 50% , Z908 VH can function as a Thin Organic Coating (TOC) . This opens up possibilities for combination:
Non-Chrome Passivation + TOC
Instead of focusing solely on corrosion resistance, the treatment system can simultaneously aim for:
- Minimize fingerprints.
- Maintain a clean and uniform appearance.
- Helps reduce friction.
- Improve machining capabilities.
This approach aligns with the trend of reducing and eliminating chromium in modern surface treatment chemicals.
View product details here ⇓
Passivation is not just a processing step – it is a determining factor in the surface quality of ZAM.
ZAM steel is developed to enhance corrosion resistance thanks to its Zn–Al–Mg coating. However, to maximize the value of the coating, post-coating surface control remains a crucial requirement.
Passivation helps create a protective transformation layer, limiting direct interaction between the metal and the environment. When combined with TOC technology, the treatment system can also be expanded to meet increasingly important market requirements such as antifingerprint, appearance, friction, and formability .
Therefore, the choice of chemical passivation for ZAM steel should not be based solely on the question “does it provide good corrosion protection?“ , but rather on a holistic assessment:
Plating composition → Passivation technology → Treatment layer quantity → Appearance requirements → Processing → Storage → Final intended use.
In the modern ZAM steel sheet manufacturing trend, PrimeCoat® Z838 and PrimeCoat® Z908 VH are two technological approaches that clearly demonstrate the shift from single-function processing to multi-functional surface protection systems , simultaneously meeting the requirements for protection, appearance, and machinability of the product.
ZAM passivation is not an “add-on” step after the plating process, but a crucial part of the surface quality control strategy. When properly selected and controlled, the passivation system can help ZAM steel maintain a more stable surface, enhance corrosion resistance, and meet increasingly demanding requirements for appearance, processing, and environmental performance.
In particular, the development of Cr³⁺ and Cr-free systems combined with TOC is opening up a new approach: transforming the post-coating treatment from a simple protective layer into a multifunctional surface treatment system for next-generation ZAM steel sheets .
Value Added from DK-CHEMICLAS
In addition to supplying AD CHEMICALS surface treatment chemicals , DK CHEMICALS also supports customers in optimizing production processes and improving line operational efficiency.
Key features include:
In-depth technical consulting.
Optimize production costs.
Improve product quality
Reduce the error rate in production.
Increase competitiveness in the market.
Support the deployment of environmentally friendly technologies.
DK CHEMICALS ‘ team of experts has practical experience in continuous production lines, helping customers choose the most suitable solution for each type of material and specific technical requirement. Contact us for expert advice!
DK Chemical Company Limited
Address: 50 Street No. 12, Cityland Park Hills Residential Area, Go Vap Ward, Ho Chi Minh City
Hotline: 0909678599
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