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Topcoat to E-coat adhesion problems

2003

I am Electrocoating products and applying a two component topcoat over it. Our product is in the oven 78 minutes @ 196. Top coat is urethane.

We are experiencing adhesion problems to the E-coat. E-coat is currently at 8H+ on ASTM pencil hardness test. This seems very hard. I have very little room for adjustments in the curing time and temp. of E-coat (large range of substrate thickness). Product is clean, test panels pass and topcoat paint checks ok. Have taken care of contaminations issues. Could it simply be E-coat hardness? Has anyone had this type of problem and what may be a cure?

Is the E-coat too hard and is there a way of checking hardness besides the pencil test?

Thanks,

Bill Kirkpatrick
large job shop - Greeneville, Tennessee, USA

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2006

Pl.specify type of paint & application system (whether acrylic,epoxy & cathodic or anodic)If the curing temp. & time of top coat film is high (as in your case) for thick components EMT (effective metal temp)would be high which will result either in embrittlement of ED coat or adhesion failure.
Also please check compatibility of Top coat & E-coat,Tack-o-rag quality.

NIKHIL JOGLEKAR
automotive paint shop - Pune, Maharashtra, India

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