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Haze (clouds) in cured powder coating

 

Q. Does anyone know what causes a hazing effect on cured powder finishes? We have been having this problem with all of our colors, could it be the paint and why? It is almost like big patches of clouds on the finished products. We are mostly powdering 10/10 Low Carbon cold-rolled steel.

Amy Onkalo
powder coating - Baraga, Michigan, USA


 

A. Dear Amy,

There are numerous reasons why you may be experiencing haze on your powder coated objects. However the most common cause is contamination. Again, there is a number of ways in which contamination can occur.

1. Dust contamination. This can occur in storage, spraying and in the oven. Check that when you store the powder the bags or containers are fully sealed, that when you clean down your spray equipment it is not left to dust exposure and check that your oven is clean.

2. Powder contamination. This is mainly a cause of incorrect cleaning of the spraying equipment, but can also occur if you are using two different powder systems within the same vicinity. E.g. An epoxy / polyester and an acrylic.

As well as contamination:

1. Poor film thickness control may give the appearance of excess haze. If the panel is sprayed too thick outgassing may occur

2. Poor surface preparation

3. Back ionisation caused by poor earthing and spraying too close to the object.

These are not all the possible causes but they are the most common. It does seem unlikely that the powder supplier is to blame as you are experiencing this problem with various colors.

Hope this helps,

Drew Devlin
- Lincolnshire

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July 24, 2012

A. Dear Amy,
The reasons for haze gloss are
1)Poor Dispersion durring Extrusion
2)Incompatible binder and reactant used
3)Wax base additives or incompatible additives
4)Improper selection of Fillers in formulation
6)Incompatible Additives which is dry blended in powder

Vijay Chopade
- Nasik, Maharashtra, India