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HR Aluminium Paint vs. Passivation  

August 18, 2008

I am working as an Engg Head in an Environmental industry.
We often export cages made out of 4 mm wires 6 to 7 meters long.
Due to its construction we are not able to ensure epoxy paint correctly on the surfaces.
We have gone for blue passivation.Still problems of some areas getting corroded exists.
We have changed to HR Aluminium paint.It is also not successful from corrosion point of view.
The final duty temperature is 200 deg C.

What is the right method for such jobs mainly for exporting.

Rajasekhar Darsi
Product designer - Pune, Maharashtra, India

Hi, Rajasekhar. You know what the cages are made of, but I don't, and I don't think the other readers do either. If they are plain steel, how can you blue passivate them? Are they zinc plated steel or galvanized steel? Or are they aluminum?

It would not be cheap, but they could be electroless nickel plated with good coverage. Or you could e-coat them for complete coverage, followed by your epoxy paint.

Regards,

Ted Mooney, P.E.  finishing.com Brick, New Jersey

Passivation results in oxide growth films on surfaces of Aluminium substrate which enhances its corrosion resistance. It is important to note that it is possible for the oxide growth film on the Al to be reduced or etched off on certain areas of the Aluminium surfaces by acidity of the final rinse bath particularly if rinsed from a neutral de-ionized water at about pH 4.

Bassey J. Udofot Knoxville, Tennessee