Early Rusting on Powder Coated Fencing

We manufactured a fence system and had the panel powder coated. The panels are made of welder wire mesh, held in place with an angle iron with a leg out onto a flat plate that is on the other side of the mesh. The mesh was welded to the angle iron and then the plate and angle iron were welded together. We installed about 900 linear feet of this fence and all the panels have rusted.

What can be done to stop the rusting? What design changes can be made to the fence panels to stop the rusting? Should the powder coating have fully encapsulated the edge detail?

Yes, there is indeed a reason for this rust. A likely cause for corrosion at the locations you mentioned is called the Faraday Cage effect. Powder coatings are applied electrostatically, and the charged powder particles deposit on the nearest grounded surface. They do not penetrate much into recesses where the plate and wire mesh are welded together. The same lack of coverage tends to occur at points where wires cross in the mesh. Since the powder coating is thin or missing in those spots, early rusting will be seen, as you have discovered.

You can change the construction details or materials as one major redesign, or you can change the coating method to dipping, chemiphoretic coating or electrodeposition coating. Spraying non-electrostatically with liquid paint would lessen the problem, but again it will be tough to get paint into all the myriad recesses.

Cleaning Zinc Phosphate Buildup

How can I clean a stainless-steel pipe that has zinc phosphate buildup inside and outside?

It can be mechanically sanded or grit blasted off. Immersion in chromic acid will also remove phosphate coatings.

Waterborne Latex Not for Traffic

Recently my supervisor asked me to take over the yellow striping of the heavily traveled parking lot where I am the maintenance person for all types of work. I'm not familiar with the various types of paint products used to stripe the asphalt area. Also, I was not well informed by the person I purchased paint from for this purpose. Consequently, I used water-based latex paint and the stripes are wearing off after two days of use. The area is heavily used by large trucks and cranes, and the yellow lines are crucial to their safe operation. Please advise.

Why you were not advised to use paints made specifically for stripe marking is strange, unless the person was avaricious or not sufficiently kind to admit they didn't know enough to properly advise you.

Most traffic marking paint is acrylic latex or acrylic-vinyl acetate latex. These dry rapidly, a major advantage for obvious reasons. Your local commercial painting supply store will certainly handle them. Ask for "traffic marking paint" and they will likely have six or more different paints available. As an example, Sherwin-Williams alone makes at least eight different formulations of traffic marking coatings. You can also do a Web search using "traffic marking paint" for additional options.

Poor Cleaning Probable Culprit in Cratering

I am having a problem painting ABS components for a two-wheeler company. There are a lot of craters where even primers are getting stuck. We have tried many things, but all in vain. Can you help?

ABS (acrylonitrile-butadiene-styrene terpolymer) is one of the easiest plastics to paint and is seldom the root cause of the defect you are experiencing. It is abundantly clear that you have a contamination problem here, possibly from poorly cleaned parts that have residual hydrocarbon or silicone oil on them when being painted. Another source of these crater-causing materials may be your paint or the compressed air supply. From halfway around the globe I cannot be sure the ABS has not been inadvertently fouled by oil or silicone, but I suspect other sources are at fault.

Carefully clean several parts very thoroughly with acetone or similar solvent, and then paint them as you normally would. If no craters appear, then poor cleaning is the most probable cause of the defects. But if craters still are evident, the contamination may be either in the compressed air or in the bulk paint itself. Only if you are certain that parts are clean and that the compressed air and the coatings are not contaminated should you investigate the possibility of the ABS having been contaminated.

More on Friction-Reducing Coatings

I was forwarded a question about friction-reducing coatings asked by a naval architect in your column. Apparently these coatings are not familiar to these end users or to you. My company holds patents for such hydrophilic coatings, which are routinely used in the medical markets for ease of insertion and leaching of antimicrobials and drugs. In fact, we also supply the recreational boating market with a temporary "go fast" coating that is hydrophilic. We wondered if you would like some commentary on these coatings? Of particular interest were the thoughts put forward by the NPCA group that met in Virginia Beach with a large contingent of Navy and Coast Guard personnel about marine and offshore coatings. Please advise if we can help in this matter.

Thank you very much for your response with information on this topic. Many readers would certainly be interested in learning more about such coatings and hearing comments concerning their usage. I'm eager to find out the specifics of their performance.