Cover paint over Arc Spray (Zn)

[mgiani84]

I´m studying the possibility of aply Arc Spray with Zn over a carbon steel tank. After that we have to aply an organic cover paint over the Zn.
Do you think that the surface will be the most suitable for the cover paint?
Have anyone some experience doing this kind of combination?

Thanks for your attention.

Mikel

 

[gr2vessels]

giani,
It is a good practice to provide additional protection for your investment of Zn arc spraying, if you can afford it. It mostly depends on your particular application. It would normally, extend the life of zinc coating considerably, particularly in an aggressive environment. Off-shore platforms using super duplex vessels for process requirements are commonly aluminium thermally sprayed on external surfaces and then apply an additional paint, typically a silicone type of coating system, for extended life. I have seen recently a super duplex high pressure separator, uncoated with severe cracks on various location, not from the internal process attack but from the external chloride attack.
cheers,
gr2vessels

 

[SJones]

Assuming that we are discussing exterior coating, take a look at AWS C2.18 and Corrosion, Vol.62, (7), 2006, pp635-647

Steve Jones
Materials & Corrosion Engineer

http://www.pdo.co.om/pdoweb/

 

[unclesyd]

We used Arc Sprayed Zn and Al on our CS drip cooler coils that used brackish water as the cooling medium. Over the years we tried various top coatings seeking to enhance the life of a coil. We were essentially unsuccessful in this attempt due to several problems with the main one being the rough surface of the AS material.
We did achieve some success with a clear coating form Carboline but it was a pain to put on an couldn't take any process temperature excursions.
As our work with these coatings occurred several years ago there are probably newer materials that could do the job.

One thing I did learn during this time is that for maximum effectiveness of the AS coating one didn't want to disturb the as sprayed surface.