Blisters

[MemphisDepay]

Hello guys,

This is an incinerator burner nozzle section.I can find a blisters at some location.What might be causing it? Is it because of painting?

 

[IRstuff]

Can you pop them? Is the paint supposed to survive the temperatures? It looks like the paint is discolored, which might suggest that the temperature is exceeding the paint's limit.

TTFN
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[MintJulep]

What might be causing it?

Poor cleaning and surface preparation before painting.

 

[Compositepro]

Since this is a burner nozzle a very likely cause is over heating of the paint. Perhaps the wrong paint was selected for this application.

 

[EdStainless]

Those are about the only options;
Wrong paint and/or exceeding temp limits, or poor surface pres and/or curing.

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P.E. Metallurgy, Plymouth Tube

 

[MemphisDepay]

Dear all,

I was not able to pop them because it was at higher elevation.

So this is because of painting failure and not because of improper material selection/ material deterioration at high temperatures?

 

[IRstuff]

"So this is because of painting failure and not because of improper material selection/ material deterioration at high temperatures?"

Not sure where you get that; at least two posts talked about wrong paint or overtemp

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[EdStainless]

You need to mount a sensor and data logger on this location so that you know the actual temperatures.
Then you can decide if the correct coating was selected.
I am suspicious of the surface prep because of the location of the blisters, but if was the coater and you complained to me I would say that clearly you took it too hot.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[IRstuff]

The paint shows a marked increase in redness in areas around the weld, compared to the part in the lower portion of the image. Color analysis shows actual reduction in blue and green intensities, making it look redder. But losing the blue and green would suggest a significant overtemperature condition, but discoloration can also be due to contamination or bad surface prep, particularly with respect to drying of the surface.

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[WKTaylor]

MemphisDepay...

Is the paint a silicon-alkyd base high-temp paint?

These 'paint blisters' look as if they may have nucleated at/near weld-spatter sites that were incompletely ground-down and/or not 100% cleaned-off.

NO paint will adhere to a 'dirty' surface; and will only partially adhere to a surface with discontinuities such as weld -spatter, dust , rust, etc. NOTE: a surface that is contaminated with trace moisture might have this same appearance... especially after a warm/hot coating cure.

Even if completely clean using chemical or steam methods, weld spatter [or any other raised surface particulate] will generally cause paint-coatings [with high solids/pigments] to 'bridge' [create a small air void/cavity at/around these raised/pinpoint details]. Voided paint [IE; with pockets of air and/or moisture] may be expanding due to heat [and joining many small voids together?] without popping/tearing the paint blisters.

Suggest using a stiff long weld rod [sharpened to a point] to poke at these 'blisters'.

Regards, Wil Taylor

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[weldstan]

The blistering appears to be along a weld. Is it/