Drilling metal - protecting from rust

[RJH]

I need to drill a few holes for self tapping screws through painted metal on my van. Some are into an enclosed cavity. What's the best way to protect the drilled metal from rust?

[Chris Green]

Spray with Owatrol or some such, before and after putting the screws in.

[alan_m]

If you paint it with anything the self tapper is likely to cut through the layer so I would use grease.

[Brian Gaff]

Even then the moisture can get in under the head, and the self tapping action tends to remove anything used to protect the metal as it screws in. Brian

[RJH]

Thanks - that appears to be the way. I had thought about flooding the cavity with waxoyl but that and such things (like Owatrol) are too expensive for this use - only 4 screws. I'll douse with grease and cross fingers . . .

[Chris Green]

That's why I said spray before and after, Owatrol works by being very penetrating and it should seal the 'post screwing' activity pretty well.

[Chris Green]

A spray can of Owatrol is an handy thing to have around anyway. :-)