WATERMARKS IN POWDER COATINGS

[Guesty]

We currently powder coat our steel products. Before they are coated they are cleaned in a Mecwash machine. We are experiencing problems in the way of water sitting in hidden parts and only becomes noticable once coated. We currently sending parts through the oven before coating and then back through the oven once the powder is applied- doubling our cycle time. Does anyone know of a way to eliminate this water contamination and cutting our cycle time down without heavy investment?

 

[WillRimmeR]

Guesty, I assume that your machine is loaded with some form of cleaning material, either an alkali cleaner or a neutral cleaner ? If a no-rinse neutral cleaner, try simply increasing the temperature allowing the high temperature picked up by the metal substrate to help flash-off the water - you can further improve this by adding hot air, with good air movement, a bit like a hair dryer, it will spread and thin the water film allowing for better, faster drying.Check with your chemical supplier to avoid compromising the chemical parameters. If you have an alkali cleaner, this almost certainly wil have a water rinse afterwards and you can normally safely increase the temperature of the rinse to dry off as mentioned before without affecting the cleaning efficiency.
Good Luck !

 

[Guesty]

WillRimmeR,

Thank you for your response. We are currently investigating higher temperatures to flash off the water, in the form of adding an IR oven into the process. Another test we are trying is drying the components in a vacuum - this lowers the temperature the water boils off at but may proven too expensive. I hadnt thought of reversing the air flow - instead of a vacuum a 'hair dryer process' I will lok into this idea. Many thanks for your help, - Guesty

 

[tim2003]

Do you have air blowoff between the washer and the dry off oven? Also, your wash chemical supplier may have rinse-aids which you can add to your washer which help de-water the surface. Be careful with this stuff - it can cause surface tension issues on your parts and can stimulate bacteria growth in your wash water.