Spray Pretreatment System

Spray Pretreatment for Powder Coating Lines

Clean, activate and protect your parts before powder coating with a spray tunnel engineered around your products, chemistry and line layout.

3–9 stage spray tunnels for steel, galvanized steel and aluminium
Compatible with iron / zinc phosphate and nano-ceramic systems
Integrated with overhead or floor conveyors as one complete line

View Typical Configurations Send Your Part Drawings

Running in 3+ countries

What Is a Spray Pretreatment System?

A spray pretreatment system is a closed tunnel that uses heated chemicals and high-pressure nozzles to clean and prepare metal parts before powder coating. Workpieces move through several zones on a conveyor, passing through degreasing, rinsing and conversion coating stages.

Compared with manual cleaning or single-tank washing, spray pretreatment gives more consistent surface quality, better coating adhesion and predictable, repeatable results for industrial production.

Typical Process Steps

• Alkaline degreasing / cleaning
• Water rinsing (1–2 stages)
• Phosphate or nano-ceramic coating
• Final rinse (DI / RO)
• Dry-off oven

Main Benefits

• Stable and repeatable quality
• Strong coating adhesion
• Improved corrosion resistance
• Suitable for continuous production

Spray Pretreatment Tunnel Layout

Degreasing Zone

Rinse Zones

Conversion Coating

Dry-off Oven

*Illustrations are for layout explanation. Actual design will be customised for your product size and line speed.

Typical Ketu Spray Pretreatment Configurations

From compact entry-level washers to high-performance multi-stage tunnels, we design each system around your substrate, corrosion requirements and available space.

3-4 stage compact spray pretreatment line

3–4 Stage Compact Line

For small factories or job shops with limited space and indoor steel parts.

• Degrease spray
• Rinse / combined rinse + passivation
• Optional dry-off oven

Best for: basic indoor furniture, simple steel components.

5–6 Stage Iron Phosphate Line

7–9 Stage High-Performance Line

For aluminium profiles, outdoor products and heavy-duty applications with strict salt spray requirements.

• Degrease, derust / pickling
• Multiple rinses
• Phosphate or nano-ceramic coating
• DI / RO final rinse
• Dry-off oven

Best for: aluminium profiles, façades, outdoor cabinets, export projects.

Substrates & Applications

Ketu spray pretreatment systems are engineered for different metals and industries. We select the process and chemistry according to your substrate and corrosion target.

Substrates

• Mild steel
• Galvanized steel
• Aluminium & aluminium alloys
• Mixed metals (with proper chemistry)

Typical Industries

• Metal furniture & garden furniture
• Electrical cabinets & switchgear
• Machinery frames & welded parts
• Aluminium profiles & building hardware

Need to run both steel and aluminium on one line? We can design a process window and chemistry combination for mixed production.

Discuss Your Substrate Mix

Key Design Features of Ketu Spray Pretreatment

We don’t just supply tanks and pumps. We engineer a complete system that is stable, clean and easy to maintain for many years of operation.

Tunnel & Tank Construction

Fully welded steel structure with chemical-resistant lining, insulated walls and large access doors for easy cleaning.

Spray Nozzle System

Nozzle layout optimised to your part geometry and conveyor speed, with quick-change nozzles and adjustable angles.

Pumps, Piping & Filtration

Industrial pumps with stainless steel or PP piping (depending on chemistry) and filtration to reduce sludge and extend bath life.

Ventilation & Mist Control

Exhaust and mist control to improve workshop environment and reduce carry-over between stages.

Control & Monitoring

Temperature and level control for each tank, with optional pH and conductivity monitoring and integration into your line PLC.

Example: nozzle and pump layout illustration for a 5-stage iron phosphate line.

Welded tank body with insulation and access doors.

Control cabinet with temperature and level monitoring.

Energy, Water & Chemical Saving Options

Ketu designs spray pretreatment systems with long-term running cost in mind. We can integrate different options to reduce energy, water and chemical usage.

Heat recovery using exhaust air or hot water loops to pre-heat incoming baths.

Zoned heating and insulation to keep temperature stable with lower energy consumption.

Rinse cascade design so the last rinse overflows into previous stages to reduce fresh water usage.

Filtration & sludge management to extend bath life and reduce chemical waste.

Automatic dosing systems to keep concentration stable and avoid over-dosing chemicals.

Example: Water & Energy Flow Concept

Rinse cascade and heat recovery illustration

Diagram only for explanation – actual design will be adjusted to your local water, gas and electricity costs.

Integrated with Your Powder Coating Line

Every Ketu spray pretreatment system is designed as part of the complete powder coating line, not as a standalone machine.

• Conveyor type and speed (overhead, power & free, floor conveyor)
• Workpiece size, hanging method and loading / unloading ergonomics
• Distance to powder booth and curing oven
• Factory columns, doors and existing equipment

Typical layout: loading → spray pretreatment → dry-off oven → powder booth → curing oven → unloading. We adjust the layout to your building drawing.

Typical Technical Range

Final specifications will be customised according to your drawings and production plan. The range below gives a typical reference:

Workpiece Size

Up to ~2000–2500 mm height, 600–1000 mm width and 3000–6000 mm length (custom sizes available).

Line Speed

Typical 0.5–3.0 m/min continuous conveyor, set according to your stage time and production capacity.

Operating Temperature

Degreasing 40–60°C, phosphating / nano-ceramic 40–55°C, final rinse ambient or slightly heated.

Materials

Mild steel with lining, stainless steel for critical zones, PP or stainless piping depending on chemistry.

Ketu Spray Pretreatment Project Snapshots

A few examples of how we configure spray pretreatment systems for different industries. Once your line is running, we can also present your project as a case study.

Furniture Factory – 5-Stage Iron Phosphate

Outdoor chairs and tables with 5-stage spray tunnel + dry-off oven + automatic powder line.

Result: improved adhesion, reduced powder defects, better corrosion performance for export.

Electrical Cabinet Manufacturer – 7-Stage Line

Degrease, derust, phosphating and DI rinse for outdoor switchgear enclosures.

Result: stable outdoor performance and improved salt spray test hours.

Aluminium Profile Producer – Nano-Ceramic Process

Multi-stage spray tunnel with nano-ceramic conversion coating for architectural profiles.

Result: thin eco-friendly coating layer with excellent paint adhesion.

Planning a new powder coating line or upgrading an old washer?

Send us your part drawings, production requirements and factory layout. Ketu will design a complete spray pretreatment concept for you.

Contact Ketu Engineering Team

FAQ – Spray Pretreatment for Powder Coating

Answers to common questions we receive from factories planning or upgrading their powder coating lines.

1. Do I really need a spray pretreatment line for powder coating? →

If you produce industrial parts regularly and need stable quality, the answer is almost always yes. Spray pretreatment gives much better cleaning and adhesion than manual wiping or single-tank washing, especially for oily and welded parts.

2. What is the difference between spray pretreatment and immersion (dip) pretreatment? →

Spray pretreatment uses high-pressure nozzles in a tunnel, ideal for continuous conveyor lines and higher throughput. Immersion pretreatment uses tanks and baskets, suitable for very heavy or complex parts and small batches. We can help you choose based on your product mix.

3. How many stages do I need for my products? →

For indoor steel, 3–4 stages may be enough. For outdoor and export projects, we usually recommend 5–7 stages with phosphate or nano-ceramic. Aluminium and heavy-duty applications often need 7–9 stages. We will design this based on your corrosion requirements and budget.

4. Can one spray line handle both steel and aluminium? →

In some cases yes, with the right chemistry and process design. However, if aluminium volume is high or quality requirements are strict, we may recommend a dedicated process or separated production windows. We will analyse your product mix and suggest the best option.

5. Which chemicals can your spray pretreatment system work with? →

Our systems can be used with alkaline degreasers, iron and zinc phosphate products, and modern nano-ceramic / zirconium coatings. We can cooperate with your existing chemical supplier or recommend partners in your region.

6. How do you control the quality of the pretreatment process? →

We use temperature, time, concentration and spray pressure as key parameters. Optional online monitoring (conductivity, pH) together with regular laboratory testing helps keep each bath within specification and ensures stable quality.

7. What information do you need to design my spray pretreatment system? →

We usually ask for workpiece drawings and photos, maximum size and weight, expected production capacity (pieces or m² per hour), available workshop space and layout, substrates, and corrosion requirements (for example salt spray hours or outdoor environment).

8. Can you upgrade an existing manual or old pretreatment system? →

Yes. We can study your existing washer and propose upgrades such as new stages, improved nozzle layout, better filtration or connection to a new conveyor and powder line. In many cases, this is a cost-effective way to improve quality.

9. How long does installation and commissioning take? →

The exact time depends on line size and site conditions, but after equipment arrives, installation and commissioning normally take several weeks including steel structure, piping, electrical works and trial production.

10. How do I maintain a spray pretreatment tunnel? →

Routine maintenance includes sludge removal, filter cleaning, checking nozzles and pumps, monitoring bath concentration and regular tank cleaning. Ketu will provide a maintenance schedule and operator training for your team.