Voids in Ecoat on Castings

How do we fix cracks in the castings?


Facebook Share Icon LinkedIn Share Icon Twitter Share Icon Share by EMail icon Print Icon

Q. We electrocoat small gray iron castings for a third party company. Sometimes the castings have small cracks and voids that fill up with liquids and create visual electrocoat paint defects. We have tried increasing the film thickness and degassing the castings before ecoat, but we don't see much improvement. Do you have any suggestions?—J.W.

A. Since there are no pictures of what you refer to as “small cracks and voids,” it is hard to gage the size, occurrence and frequency of the casting defects.

For workable sized crack and voids, you can try filling them with a suitable casting filler or putty. Since you will be electrocoating the casting, it is necessary that a conductive filler or putty be used, or it will not be electrocoated. Also, the putty must be capable of withstanding typical electrocoating cure temperatures of 350-400°F.

Conductive putties typically contain high levels of zinc or aluminum powder particles mixed in with epoxy or acrylic resin materials that can make them cure and harden.

One thing to mention is that unless fully cured, the putty can leach unwanted chemicals into your critical pretreatment or electrocoat tank, interfere with pretreatment or ecoat stages or lose hardening performance.

You should ask your pretreatment and electrocoat suppliers for recommendations on putty or filler products they have experience working with, and are known to be compatible with your process and their materials.  

Related Topics


  • Measuring the Surface Area of Fasteners

    How do you measure the surface area of a threaded fastener? How much coating would you put on it? How thick of a coating? What about non-threaded fasteners? The U.S. Department of Agriculture’s Forest Service, of all people, may have come up with the solution for those pondering how to coat sometimes-difficult small pieces using computer imaging and software to compute the area.

  • Waterborne painting process is a first at South Carolina BMW plant

    PPG launched the first use of waterborne compact paint technology in a U.S. automotive manufacturing plant at the BMW assembly plant in Spartanburg, S.C. This painting process has turned out to be a 2012 award winner and has opened up a new way for auto manufacturers to go leaner and become more efficient in their operations.

  • 40-Under-40: Class of 2016

    Young professionals are a vital asset to the finishing industry. Products Finishing is recognizing the industry’s top young talent through an annual 40-Under-40 program.