TL;DR
Blocked pretreatment nozzles leave bare metal areas that fail E-coat adhesion. Inspect and clean nozzles at scheduled intervals and confirm spray coverage before production.
What you might see
- E-coat adhesion failures on specific body areas
- corrosion in localized areas after salt spray testing
- individual spray nozzles with no visible spray during operation
- pretreatment stage pressure drop higher than normal
Likely causes
Nozzle orifice blocked with scale, phosphate deposits, or particle contamination
Nozzle tip eroded changing the spray angle and reducing coverage
Supply line strainer blocked upstream of the nozzle bank
Low pump pressure reducing flow to the nozzle zone
Required tools
- Chemical-resistant gloves, face shield, and protective suit
- Descaling solution compatible with pretreatment chemicals
- Wrench for nozzle removal
- Strainer cleaning brush
- LOTO kit
Safety first
- Pretreatment chemicals are corrosive and some stages use acid solutions. Always wear chemical-resistant PPE. Have an eyewash station accessible.
- Lock out spray pumps before accessing nozzle banks. High-pressure chemical spray causes chemical burns and eye injury.
Procedure
- 1
Lock out the pretreatment line before accessing the spray nozzle zone.
Warning: Pretreatment chemicals include phosphate acid solutions and alkaline cleaners. Wear chemical-resistant gloves, face shield, and full body protection when working with pretreatment sprays. - 2
Identify the blocked nozzles by visual inspection during operation from a safe observation position, or by checking spray coverage on test panels.[1]
- 3
Remove the blocked nozzle tips by unscrewing them from the nozzle body.
- 4
Soak the nozzle tips in a descaling solution appropriate for the pretreatment chemical used. Do not use wire tools to clear nozzle orifices as this distorts the spray pattern.[1]
- 5
Inspect the supply line Y-strainer upstream of the nozzle bank. Clean the strainer screen if blocked.
- 6
Reinstall clean nozzles, restore power, and perform a spray pattern check on a test sheet before processing production parts.
Sources
Dürr Dürr EcoPaint E-Coat E-Coat / Pretreatment Line general technical documentation, Dürr
Durr EcoPaint E-Coat pretreatment system maintenance documentation (general)
More guides for Dürr Dürr EcoPaint E-Coat
How to diagnose rectifier voltage faults on a Durr EcoPaint E-Coat line
Rectifier faults interrupt the E-coat deposition process. Check the rectifier input voltage, cooling system, and output connection before suspecting an internal rectifier failure.
How to correct tank chemistry out of specification on a Durr EcoPaint E-Coat line
E-coat film defects are almost always traceable to bath chemistry drift. Check pH, conductivity, and bath solids concentration against the bath specification before adjusting electrical parameters.
Stop fixing the same fault twice.
Dovient turns guides like this into your team's shared playbook, with AI that catches recurring issues before they break the line.