Talk Composites - The Forum for Advanced Composites

Pin holes appearing using GC50

http://www.talkcomposites.com/Topic18931.aspx

By MarkMK - 8/5/2015 9:18:37 AM

Hi All

A couple of recent parts have come out with pin holes all over. Both received a good coat of GC50 sprayed before infusion under full  (and drop tested) vacuum.

Clearly there's very little time to allow the coating to de-gas prior to spraying, so wondering if it might be an issue with the gun/compressor causing this?

Anyone experienced similar?

Thanks
By MarkMK - 8/5/2015 2:21:08 PM

It won't let me add pics direct, so I've posted a link to one I've just taken. Not easy to get a decent shot on the curved surface, but hopefully you'll see enough.

https://www.dropbox.com/sc/xcnvm2s76i55stm/AADevknoAgaM9O2JbENvSGWBa

If you zoom in the surface looks horrendous, but perhaps the crater-like appearance is just normal and we don't usually zoom in that much, but the little holes are concerning.

I sprayed another couple of parts at the same time as this one and haven't experienced the same issue with those, so a bit baffling. I believe I laid down the coat pretty consistently and it was left overnight before layup the next day. From a few feet away all looks nice and glossy, but didn't expect this from an in-mould coating. No humidity or cold issues that I can think of either.

I did use a small amount of Aerofix3 to help position, but all I've seen previously is the occasional dull spot from this where I might have not misted the spray quite carefully enough.

Not the easiest thing to do with the cup gun, but I will try to do a gentle mist coat first and leave for a couple of minutes before adding more, to see if that helps eliminate this