What Is Powder Coating?
Powder coating is a dry finishing process where finely ground particles of pigment and resin are electrostatically charged and sprayed onto a metal surface. The coated part is then baked in an oven at 180-200 degrees Celsius, causing the powder to melt, flow, and cure into a hard, durable, uniform film.
Unlike traditional liquid paint, powder coating contains no solvents and emits near-zero volatile organic compounds (VOCs). The result is a finish that is thicker, more uniform, more durable, and more environmentally friendly than wet paint — which is why it has become the industry standard for sheet metal fabrication worldwide.
How the Powder Coating Process Works
The complete process involves five steps, each critical to achieving a quality finish that lasts.
Step 1: Surface Preparation
This is the most important step. Poor preparation is the number one cause of coating failure. The process includes:
- Degreasing — Alkaline wash removes oils, coolant residue, and fingerprints from fabrication
- Rust removal — Acid pickling or mechanical abrasion removes any surface oxide
- Phosphating — Iron or zinc phosphate conversion coating creates a crystalline layer that dramatically improves adhesion and corrosion resistance
- Rinsing — Deionized water rinse removes all chemical residues
- Drying — Parts are dried completely in an oven before coating
For stainless steel and aluminum, the phosphating step is replaced with specialized pretreatments (chromate-free conversion coating for aluminum, or passivation for stainless).
Step 2: Masking
Any areas that must remain uncoated — threaded holes, mating surfaces, electrical contact points, bearing surfaces — are masked with high-temperature tape, silicone plugs, or custom metal masks before spraying.
Step 3: Electrostatic Spraying
The powder is loaded into a spray gun that imparts a positive electrostatic charge to each particle. The metal part is grounded, so the charged powder particles are attracted to and cling to every surface of the part — including edges, corners, and recesses.
This electrostatic attraction is what makes powder coating so uniform compared to liquid paint, which tends to sag on vertical surfaces and pool in recesses.
Step 4: Curing
Coated parts enter a curing oven at 180-200 degrees Celsius for 15-25 minutes (depending on powder type and part mass). During curing:
- Powder particles melt and flow together into a continuous film
- Chemical cross-linking occurs, creating a thermoset polymer
- The coating reaches its final hardness, adhesion, and chemical resistance
Step 5: Cooling and Inspection
Parts cool to room temperature and are inspected for:
- Film thickness — Measured with a magnetic gauge (target: 60-80 microns standard)
- Adhesion — Cross-hatch tape test per ISO 2409
- Visual defects — Orange peel, runs, thin spots, contamination
- Color match — Compared against RAL standard chip
Powder Coating vs Wet Paint
| Property | Powder Coating | Wet (Liquid) Paint |
|---|---|---|
| Film thickness | 60-120 microns (single coat) | 25-50 microns per coat |
| Coats required | Usually 1 | Usually 2-3 (primer + topcoat) |
| Durability | Excellent (impact, scratch, chemical) | Good to moderate |
| UV resistance | Excellent (polyester powders) | Varies by paint type |
| Corrosion resistance | Excellent (with proper pretreatment) | Good (with primer) |
| Edge coverage | Excellent (powder wraps edges) | Poor (paint pulls away from edges) |
| Environmental | Zero VOC, overspray recycled | High VOC, solvent emissions |
| Color consistency | Very uniform (electrostatic) | Depends on operator skill |
| Minimum order | Practical from 10+ pieces | Practical from 1 piece |
| Setup time | Moderate (color change = booth cleaning) | Quick (gun change) |
| Cost (per m2) | Lower for production volumes | Lower for 1-5 pieces |
| Touch-up | Difficult (requires re-bake) | Easy (brush or spray) |
When to choose powder coating: Production batches of 10+ pieces, parts that need maximum durability, outdoor applications, food-safe requirements, or when environmental compliance matters.
When to choose wet paint: Single prototypes, parts too large for the oven, parts with tight color-match requirements to existing wet-painted surfaces, or when field touch-up capability is essential.
Types of Powder Coating
Not all powder coatings are the same. The resin system determines the coating’s performance characteristics:
| Powder Type | Cure Temp | UV Resistance | Chemical Resistance | Flexibility | Best For |
|---|---|---|---|---|---|
| Polyester (TGIC) | 180-200°C | Excellent | Good | Good | Outdoor, architectural |
| Polyester (HAA) | 180-200°C | Excellent | Good | Good | Outdoor (TGIC-free) |
| Epoxy | 180-200°C | Poor (yellows) | Excellent | Good | Indoor, chemical environments |
| Hybrid (epoxy-polyester) | 180-200°C | Moderate | Good | Good | Indoor general purpose |
| Polyurethane | 180-200°C | Excellent | Excellent | Excellent | Automotive, premium |
| Nylon | 200-220°C | Good | Good | Excellent | Functional (anti-friction) |
Our standard: We use polyester (TGIC or HAA) for most jobs because it provides the best all-around performance — excellent UV resistance for outdoor use, good chemical resistance, and the widest color range. For purely indoor applications, we offer hybrid powder at a lower cost.
RAL Color System
RAL is the international color standard used for powder coating. There are over 200 standard RAL colors, but in practice, about 30 colors account for 95% of all orders.
Most Popular RAL Colors for Sheet Metal
| RAL Code | Color Name | Common Applications |
|---|---|---|
| RAL 7035 | Light Gray | Electrical enclosures, machine covers |
| RAL 7032 | Pebble Gray | Industrial equipment |
| RAL 9003 | Signal White | Medical, clean environments |
| RAL 9005 | Jet Black | Consumer electronics, displays |
| RAL 9010 | Pure White | Interior fixtures, lighting |
| RAL 7016 | Anthracite Gray | Architectural, premium |
| RAL 5015 | Sky Blue | HVAC, utility equipment |
| RAL 1023 | Traffic Yellow | Safety guards, barriers |
| RAL 3020 | Traffic Red | Fire equipment, safety |
| RAL 6005 | Moss Green | Outdoor furniture, agricultural |
| RAL 2004 | Pure Orange | Warning indicators, accents |
| RAL 7040 | Window Gray | Telecom cabinets |
Texture and Gloss Options
Beyond color, powder coating offers texture and gloss variations:
| Option | Description | Use Case |
|---|---|---|
| Smooth gloss (>80 GU) | Mirror-like, shows surface imperfections | Consumer products, indoor |
| Semi-gloss (40-60 GU) | Subtle sheen, hides minor imperfections | General industrial |
| Matte (10-30 GU) | Flat, no reflection | Premium/architectural, military |
| Fine texture | Slight orange-peel surface | Hides weld marks, sheet imperfections |
| Coarse texture (wrinkle) | Pronounced textured surface | Heavy equipment, vandal-resistant |
| Metallic | Contains metallic flakes | Decorative, automotive-style |
| Antimicrobial | Contains biocidal additives | Medical, food service, public spaces |
Our recommendation: Semi-gloss smooth finish is the best default choice — it looks professional, hides minor sheet metal imperfections, and is easy to clean.
Pricing Guide 2026
Powder coating pricing depends on part size, complexity, surface preparation requirements, and quantity. Here are reference prices for standard polyester powder coating with zinc phosphate pretreatment.
Pricing by Part Size
| Part Size Category | Example Parts | Price per Piece (VND) |
|---|---|---|
| Small (under 0.05 m2) | Brackets, clips, small covers | 8,000 - 15,000 |
| Medium (0.05-0.2 m2) | Enclosure panels, equipment covers | 15,000 - 35,000 |
| Large (0.2-0.5 m2) | Machine guards, large panels | 35,000 - 70,000 |
| Extra large (0.5-1.0 m2) | Enclosure bodies, cabinets | 70,000 - 150,000 |
| Oversized (>1.0 m2) | Full-size cabinets, frames | 150,000 - 350,000+ |
Pricing by Area (for estimating)
| Surface Preparation | Coating Type | Price per m2 (VND) |
|---|---|---|
| Standard (degrease + phosphate) | Polyester smooth | 80,000 - 120,000 |
| Standard (degrease + phosphate) | Epoxy-polyester hybrid | 70,000 - 100,000 |
| Heavy prep (rust removal + phosphate) | Polyester smooth | 100,000 - 150,000 |
| Aluminum prep (chromate-free) | Polyester smooth | 90,000 - 130,000 |
Quantity Discounts
| Quantity | Discount |
|---|---|
| 1-10 pieces | Base rate |
| 11-50 pieces | 10-15% off |
| 51-200 pieces | 15-25% off |
| 200-500 pieces | 25-35% off |
| 500+ pieces | 35-45% off |
Additional Cost Factors
| Factor | Impact on Price |
|---|---|
| Non-standard RAL color | +10-20% (special powder order) |
| Metallic or textured finish | +15-30% |
| Second color (two-tone) | +60-100% (requires masking) |
| Extra masking (threads, surfaces) | +5,000 - 20,000 per piece |
| Rush order (2-3 day turnaround) | +30-50% |
| Premium powder (Akzo Nobel, Tiger) | +10-20% vs economy brands |
All prices are reference estimates. Actual pricing depends on your specific parts and requirements.
Limitations and When Not to Use Powder Coating
Powder coating is not universally applicable. Here are scenarios where alternatives may be better:
Size Limitations
Parts must fit in the curing oven. Our oven accommodates parts up to 2500 x 1200 x 1000mm. Larger assemblies must be coated in sections and assembled afterward, which creates visible seams.
Temperature-Sensitive Components
The 180-200 degree Celsius curing temperature rules out powder coating for:
- Assemblies containing rubber seals, plastic components, or adhesives
- Parts with press-fit bearings or bushings (thermal expansion may loosen fit)
- Electronics or PCBs
Solution: Coat individual sheet metal parts before assembling with temperature-sensitive components.
Field Repair
Powder coating cannot be touched up in the field like wet paint. Any damage requires stripping and recoating the entire part (or at minimum, an affected panel). For equipment that will be frequently scratched and needs field touch-up, consider wet paint or a durable zinc-rich primer with wet paint topcoat.
Very Tight Tolerances
Standard powder coating adds 60-80 microns per surface. For parts with mating tolerances under +/- 0.1mm, masking critical surfaces is essential. Discuss tolerance-critical features with us during the quoting stage.
Powder Coating for Different Base Materials
| Base Material | Pretreatment | Notes |
|---|---|---|
| Mild steel (SS400, SPCC) | Degrease + iron/zinc phosphate | Standard process, excellent adhesion |
| Galvanized (SGCC, SECC) | Degrease + zinc phosphate | Good adhesion, zinc provides backup corrosion protection |
| Stainless (SUS304) | Degrease + special primer | Pretreatment critical for adhesion (stainless is naturally passivated) |
| Aluminum (5052, 6061) | Degrease + chromate-free conversion | Requires aluminum-specific pretreatment for adhesion |
| Copper / Brass | Degrease + special primer | Rarely powder coated, but possible with proper prep |
Our Powder Coating Capabilities
| Specification | Value |
|---|---|
| Max part size | 2500 x 1200 x 1000mm |
| Standard film thickness | 60-80 microns |
| Thick film option | Up to 120 microns |
| Oven temperature | 180-200°C controllable |
| Color change time | ~30 minutes (booth cleaning) |
| Standard turnaround | 5-7 working days (coating only) |
| Colors in stock | RAL 7035, 9005, 9003, 9010, 7016, 7032, 1023 |
| Quality standard | ISO 2409 adhesion, ISO 2360 thickness |
Learn more about our full powder coating service.
Getting the Best Results: Tips for Designers
- Specify the RAL code, not just a color name — “Gray” is ambiguous. “RAL 7035 semi-gloss” is precise.
- Mark masking areas on the drawing — Circle any threaded holes, mating surfaces, or ground points that must not be coated.
- Allow for coating thickness in tolerances — Add 0.15mm (2 x 80 microns) to hole diameters or subtract from shaft diameters if coated surfaces mate.
- Use drain holes — Enclosed box shapes trap pretreatment chemicals. Add drain holes (6mm minimum) in low points that can be plugged after coating.
- Consider hang points — Every part needs to be hung on a rack for coating. Include or identify a non-critical area for the hanging hook contact point (this spot will have no coating).
- Design for even coating — Deep recesses and inside corners are harder to coat evenly. A minimum recess depth-to-width ratio of 1:1 ensures proper coverage.
Get a Powder Coating Quote
Whether you need coating for laser-cut panels, bent enclosures, welded assemblies, or standalone parts, we provide complete surface treatment under one roof — no need to coordinate with a separate coating vendor.
Send us your drawings with the following information for an accurate quote:
- Part dimensions and quantity
- Material type
- Desired RAL color and gloss level
- Any masking requirements
- Required film thickness (if different from standard 60-80 microns)
Contact us today for a free quote. We typically respond within 24 hours.