Rusty nails - Spot Primer

[vards01]

Does anyone have any advice on stopping rusty nails coming through on exterior paintwork. I have tried to knock them in, clean rust off with a dremel then spot prime with a zinc phosphate primer, then fill with a 2 pack......once I've painted up with zinnsser perma white, a month or so in and I have brown coming through, most frustrating! Is there a more appropriate spot primer to use....or is this really down to the water based system I'm using.

 

[Nige F]

Down to the water based, I reckon . Old Skool they would have been punched in, oil primed, stopped with linseed oil putty, oil u/c and gloss.

 

[vards01]

I was very surprised that it penetrated the zinc phosphate, especially as Zinnsser 123 was also used on top as the overall primer stating 'Excellent' rust stain properties. Is there a more appropriate spot primer on the market today, I did see the aluminium primers, but for steel / iron I didn't think it got much better than zinc phosphate?

 

[vards01]

I should also add this is on a fascia and soffit

 

[JohnD]

I've also seen this on things primed but not topcoated. I'm sure you need to dab on an oil-based topcoat, to prevent damp getting to the steel. Do any filling afterwards. You get the same indoors if you put polyfilla over steel nails.

Bear in mind that the part of the nail inside the wood will also be getting rusty.

In a coastal environment I formerly used galvanised nails outdoors, but for anything important I now use stainless screws, they have become quite cheap.

 

[vards01]

I will try the topcoat idea on the zinc phosphate.........this is an old house so short of replacing fascia and soffit I'm just going to try and work with it. I too only use stainless now on exterior work to be painted.