Hot Rolled Galvanized Steel Coils: Surface Treatment Options

 

Need hot rolled galvanized steel coils with specific surface treatments to optimize your manufacturing process? You've come to the right place. GNEE Steel offers premium hot rolled galvanized steel coils in DX51D/SGCC grades with 30g/m² zinc coating-plus a full range of surface treatments: Light Oil, Unoil, Dry, Chromate Passivated, and Non-Chromate Passivated. In this guide, we'll explore treatment benefits, compatibility with manufacturing processes, and selection criteria to help you make the best choice.

 

Galvanized steel coils

 

Surface treatments are a critical component of hot rolled galvanized steel coil performance. They enhance corrosion resistance during storage and processing, improve compatibility with secondary operations (like painting or welding), and ensure compliance with industry-specific regulations. Each treatment is applied after galvanizing, using controlled processes to maintain consistency across every coil.

 

Our surface treatments are designed to meet the needs of diverse industries, from automotive and electronics to construction and furniture manufacturing. All treatments comply with international standards, including EU REACH and RoHS directives for environmentally sensitive markets.

 

 

Each surface treatment offers unique benefits, tailored to specific storage, processing, and end-use requirements.

 

Surface Treatment	Application Method	Primary Benefit	Secondary Benefits	Processing Compatibility	Shelf Life (Indoor Storage)
Light Oil	Spray coating	Prevents storage rust	Improves lubricity for forming	Welding (no pre-cleaning needed), bending, stamping	6-12 months
Unoil	Chemical degreasing	No residue for sensitive applications	Clean surface for immediate processing	Painting, powder coating, adhesive bonding	3-6 months
Dry	Hot air drying + surface conditioning	Residue-free, moisture-resistant	Enhances paint adhesion	Food-grade applications, medical equipment components	4-8 months
Chromate Passivated	Chemical immersion	Enhanced corrosion resistance	Improves paint adhesion, prevents white rust	Electronics, marine components (non-EU markets)	12-18 months
Non-Chromate Passivated	Chemical immersion	Eco-friendly corrosion protection	Complies with EU RoHS/REACH	Automotive, EU/US consumer products	10-16 months

Chromate passivation provides the highest corrosion resistance but contains hexavalent chromium, making it unsuitable for EU markets. Non-Chromate Passivated offers a viable eco-friendly alternative with only slightly reduced performance.

 

 

We maintain consistent core dimensions and quality standards across all surface treatment options.

 

Surface Treatment	Thickness Range (mm)	Width Range (mm)	Coil Weight (MT)	Certificate Compliance
Light Oil	0.3-2.0	914-1800	5-6	BV, ISO, SGS
Unoil	0.3-2.0	914-1800	5-6	BV, ISO, SGS
Dry	0.3-1.5	914-1500	5-6	BV, ISO, SGS, FDA (food contact)
Chromate Passivated	0.3-1.8	914-1600	5-6	BV, ISO, SGS
Non-Chromate Passivated	0.3-1.8	914-1600	5-6	BV, ISO, SGS, RoHS, REACH

 

All treatments are applied in controlled environments to ensure uniform coverage. We use high-quality oils and chemicals from trusted suppliers, minimizing the risk of surface defects or compatibility issues.

 

 

Selecting the optimal surface treatment requires considering your storage conditions, manufacturing processes, and end-use requirements:

 

• Storage Duration: If coils will be stored for 6+ months before processing, Light Oil or Passivated treatments are recommended to prevent rust.
• Subsequent Processing:

Welding/bending: Light Oil provides lubrication and rust protection.

Painting/coating: Unoil or Dry treatments eliminate the need for degreasing.

Adhesive bonding: Dry surface ensures maximum bond strength.

• End-Use Regulations: EU/US markets require Non-Chromate Passivated or eco-friendly treatments to comply with RoHS/REACH.
• Environmental Conditions: High-humidity storage areas benefit from Chromate or Non-Chromate Passivation.
• Special Requirements: Food-contact applications require Dry, FDA-compliant surface treatment.

We also offer custom surface treatment combinations for unique requirements-for example, Light Oil + Chromate Passivation for long-term storage followed by welding.

 

For hot rolled galvanized steel coils with your required surface treatment-whether Light Oil, Unoil, Dry, Chromate, or Non-Chromate-GNEE Steel delivers compliant, high-quality products tailored to your needs. Our coils meet international standards, come with full certification, and are backed by our 20-year manufacturing expertise. Contact us now to discuss your processing requirements, request compatibility testing, and get a customized quote!

 

• Zinc Thickness

 

Zinc Coating Grade	Zinc Coating (g/m²)	Corrosion Resistance	Typical Applications	Remarks
Z30	30	Very low	Indoor parts, home appliance inner panels, ventilation ducts	Not suitable for outdoor use
Z60	60	Low	Indoor structures, temporary facilities	Low cost
Z80	80	Medium	Light steel structures, base metal for PPGI	Good cost performance
Z100	100	Medium	PPGI, fencing, general construction	Common export grade
Z120	120	Medium-High	Roofing sheets, wall panels	Longer service life
Z140	140	Medium-High	Industrial buildings, agricultural facilities	Suitable for outdoor use
Z180	180	High	Long-term outdoor structures, equipment housings	Recommended for outdoor use
Z200	200	Very high	Humid environments, heavy structures	Higher cost
Z275	275	Excellent	Coastal areas, solar mounting systems, high-corrosion environments	High standard

 

Request mechanical properties report + SGS test certificate