Spraying in Cavities

[Burdekin]

Hi Guys,
I’m in the middle of welding up a couple of old classics and replacing sills, outriggers, inner wing shotguns etc and would like to spray them internally with epoxy primer through drain holes and where I could get access from. Any ideas of what the best way to do this would be? I have a cavity injection spay gun, would this do the trick or is there something better out there?

 

[danelectro]

Would it not be better to just spray Waxoyl or cavity wax into those areas?

 

[mike 109444]

This stuff from Screwfix seams to work for me and it's a lot cheaper ( £ 4.00) than the weld through primer (> £ 8.00 a can) Having cleaned the metal to be welded if you then spray and in warmish weather, drys to handle in 10 to 15 mins and having welded over it I find it does not burn off or lift. Seams quite heat resistant. It's the can on the left !

 

[richie00boy]

Would it not be better to just spray Waxoyl or cavity wax into those areas?

Absolutely not! Those products have very poor protection against bare metal. Over time they dry out and crack, allowing moisture in. Cavity wax is OK if you redo it every year, but I'm not a fan of it at all. It just makes such a mess if you need to do any work.

 

[mike 109444]

Like this

 

[richie00boy]

Very nice, but how is he going to get that into internal sections like sill cavities

 

[mike 109444]

You spray them before attaching the new metal. But yes if the section is not open to be sprayed then the rust on inside would need treating before any spraying of paint or wax oil.

 

[danelectro]

Absolutely not! Those products have very poor protection against bare metal. Over time they dry out and crack, allowing moisture in. Cavity wax is OK if you redo it every year, but I'm not a fan of it at all. It just makes such a mess if you need to do any work.

Well I have to say I disagree, applied correctly and not skimped with, these products give good protection......personally i would use a good thick cavity wax over waxoyl, but i've only been doing this stuff for the last 27 years, so I probably don't have long term historical data!!!! And to be honest, if you did it right in the first place I don't think you need to do it every year, you'd end up filling the cavities with so much wax they'd be solid!!!

But yes I agree, it would have been better to paint the inside of the panels before fitting.

 

[Burdekin]

Thanks for the replies.

I apply weld through primer on the inside of repairs being welded in but weld through primer will rust through so I want to coat with epoxy primer and then cavity wax. The inner wing shotguns come premade with no primer or paint on them so spraying them internally is what I'd like to do if practical so wondering if there is a good injection nozzle or something that's good for spraying internally.

 

[vdubz]

Noxudol 700 cavity wax is good stuff. As daneletro says, you don't really want to be waxing it every year as you could end up with a sloppy mess which may hold moisture. Use a longer lasting wax(noxudol700) and do it every 4-5 years, you also want a nozzle that will produce a fine mist for a nice thin even coat.