Water Marks on Powder coated parts 1

[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 - doubling our cycle time. Does anyone know of a way to eliminate this water contamination and cutting our cycle time down without heavy investment?

 

[ornerynorsk]

We have dealt with this problem extensively. You MUST provide for complete drainage of all acid bath/prewash/phosphate bath fluids. We still run them through the oven once before powder application to insure complete dryness. I know of know other way to totally expel all moisture, which is critical to a good PC finish.

 

[Guesty]

Thank you for replying!! To reduce our cycle time we are investigating adding another oven to the line so that pre-heat can still be achieved but only takes one cycle. An alternative to this is that we are investigating a vacuum system that can remove all moisture prior to leaving the MecWash washing facility.

 

[PowderCoater]

Have you considered adding additional air blowers to the system? Air movement, not heat is sometimes the answer to removing the moisture.

 

[barmade]

We had a similar issue on a small quantity of product that had a tube in it with an entrance port. The wash solution would get into the tube and then boil out during the curing phase. The curing phase was around 400/420 F in an IR oven.The dry-off gas fired oven was around 350 F. We found that by raising the dry-off to 420 f we would boil off any of this residual solution and eliminated the water marks that were occuring at cure. It does cost us a little more for energy but this is only for a small quantity of our production.

 

[kenvlach]

Painting over the residue left by evaporation hides a potential long-term corrosion problem. Eventually, water vapor will permeate through the paint and activate the salts. Always best to have freely draining parts, as ornerynorsk recommended, but even then you may have adhering droplets. A final rinse with hot DI water aids draining, drying and avoiding residue.

Consider adding airknives to blow off rinsewater and dry the surface. In some cases, you can save drying steps and costs.

http://www.paxtonproducts.com/air.htm