Troubleshooting granular appearance of powder coated articles

A. In regard to the name Rilson I believe it should be "RILSAN" which is a NYLON 11 coating normally electrostatically applied for heavy items. A fluidised bed can be used. The Rilsan powder is made in France by ATOchem and they have agents all over the world including Australia.

Good luck,

A. Dear Mr Leo,

If you are painting, then isn't conductivity still an issue or are you selectively painting? I would recommend that you E-Coat the Aluminium housing instead of choosing to paint. Have you tried Electroless Nickel on the housing for a comparison of galvanic corrosion? Its my guess that it may eliminate GC completely.

A. I would recommend you to use a conversion treatment of the aluminium 6061 T6 like e.g. yellow Alodine 1200 S. This treatment will barely harm your electrical conductivity. As a top coating for improved lifetime, I would either paint with powder or Rilsan (Polyamide 6.6). This will give you a perfect product for outdoor applications.

A. Sorry about the long gap in reverting. As Nickel over aluminum includes a copper plating, your RF may no longer be an issue.
However the chromating option will also work. E-Coat meant CED painting.

A. Hi. E-coat or CED painting is the application of paint via a process where it is electrochemically deposited sort of like electroplating. However, because the paint is insulating after the electrochemical conversion, it covers evenly with no missed spots, theoretically no pinholes, and no concern about Faraday Cage effects. All automobiles these days are e-coated before the finish painting as a corrosion proofing step. E-coating is compatible with other coatings, so chromating followed by e-coating followed by the polyamide powder coating which Niels suggests should comprise a robust system.

Regards,

A. Rilsan is commonly used as isolation coating on plating racks. It is very resistant to chemical attack in strong acids and alkalines. Chromic acid attacks Rilsan though. From this, I would predict that as a coating it would be highly resistant. The drawback is that it is rather brittle. The coating may crack.

A. RILSAN Fine Powder, an ATOFINA Chemicals, Inc. trade name, is used as a corrosion protective coating for couplings, fittings, and pipe for both potable and sea water. It has more than 25 years of use in these environments. See AWWA C224 for its application and NSF 61 for listing of approved coatings.

A. Rilsan is a thermoplastic coating based on polyamide 11. Since more than 20 years ago, it has been used in the handling of water, waste water and sea water. For instance, it has been used to protect the piping system of cooling system in cruise built in the Netherlands.

A. First off, is it a problem that you are having, or just a question about the makeup of powder paint? There is a common problem with powder paints, called "seeding", that can cause a granular effect. It happens towards the end of the manufacturing process when the equipment is hot from running, and the paint actually starts to cure in the machine producing little grains of partially cured paint that show up quite well when applied to a smooth surface. You will usually find it in the last couple of boxes of the batch. The manufacturer will usually replace the 'seedy' paint -- you get to deal with the rejects though. I hope this is the information you were looking for.

A. Dear Sirs,

Try Polyamide 11 - Nylon. Contact your local agent for more info and samples.

A. Nylon would cover a fairly large range of powders, so I am not sure if my answer will work for you but you can give it a shot. We have done polyamide coating brand name Rilsan from Arkema very successfully. We preheat the product to a temperature where there is no requirement to reheat the coating at all. It cures by its own heat content. Each product requires its own settings but once that has been done the results are repeatable. The coating in our case is 250 to 300 microns DFT. Best of luck.

A. What kind of coating are you looking for?

Is it for the exterior body protection or is this coating for the Wear & Corrosion Resistance of valve components?

In case it is for wear and corrosion resistance, I would recommend Tungsten Carbide coatings. These are sprayed by either HVOF or Detonation spray process.

The selection of coating is also dependent on the medium in contact of valves.

A. Hello Mr.Kaushal R Shah Kaushal,

Better go for Rilsan powder coating.
This is almost similar to powder coating. This type of coating will give better performance on valves.
Up to my knowledge this cost is slightly high ... and base preparation is a must (blasting or phosphating)

Thanks, Kannan. Although the word Rilsan is sometimes used a bit generically, Rilsan® is actually a trade name of Arkema for a series of different polyamide thermoplastic coatings, including PA11 nylon coatings. I think you are probably suggesting PA11 / Nylon 11 coatings.

Hi, Kaushal. Halar® is a Solvay trade name for fluoropolymer coatings. Your exact requirements aren't fully clear to me, but fluoropolymer coatings are similar to Teflon in exhibiting exceptional chemical resistance. As far as a know, heavy thermoplastic powder coatings are applied by immersion in a fluidized bed rather than by electrostatic spray, as that is the only way that I have seen them applied. I am not really an expert in these subjects, but am just trying to steer the discussion towards the technical aspects and away from brand names because we try to avoid that (why?). Good luck.

Regards,