I have looked at some nails left over from my roofer and they are hot dipped they are better than coated for corrosion .
These were used for battens, for the slates we used copper. Not having a zinc nail in front of me I would guess they are smoother than a galvanised nail. I think the hot dipped will grip better in the timber.

Hot dipped will last forever , zinc coated nigh on as long ( so long as the actual roof covering works as it should) , if you do get a leak then the zinc coated will rust quicker. For what it’s worth- i stripped a kent peg roof a couple of years back, that had been done in 1907, done the old way where the battens where plastering lathes held on with iron nails, the tiles had been torched underneath with lime mortar, where the roof was still watertight the lathes and nails were pretty much as good as the day they’d been nailed on.

Many thanks for the replies - all very helpful stuff and in line with what I thought / what I've been reading.

It does leave me wondering though... If hot dipped are so much better, why do people choose to use (and roofing stores choose to sell) the far inferior electro zinc coated? Samac were very quick to assure that they were perfectly fine for fixing battens. They don't even make hot dipped nails...

Cheers

Greenfinger, as with most things in life people will sell anything that others are willing to buy, any self respecting roofing company will use hot dipped as a matter of course and buy them in 25kg boxes, in the cost of a roof the batten nails are a rounding error.

Just watch out for sellers trying to pretend that "galvanised" means electroplated. Like "brass" = brass plated.
(Or "Victorian" = vaguely mid 20th century look-alike"

What is scaffolding - hot or electro?

Posted By: chrisinbrightonOn a similar subject,has anyone found a supplier of hot dipped galv countersunk woodscrews?
I canly find nuts/ bolts or nails that are hot dipped

I have looked in the past and failed, nearest can get to screws is coach bolts with square or hex heads. Suspect if you hot dipped the screw the slots/drive heads would get filled but don't know if that is the reason. I would normally got to stainless and cut the thread with a conventional screw of similar size first.

As owlman says, a search shows several possibilities. Also some "Electro Galvanised" offerings. But usually woodscrews are concealed and you probably wouldn't want a galvanised one on show, so what's the advantage? A bit of surface corrosion doesn't matter.

Posted By: chrisinbrighton`woodscrews` are often used to hold guttering and downpipe clips. Ive often seen brown streaks down white rendered walls from zintec screws.
I guess stainless is an option but they are very soft

I have only stainless screws exposed on our build. Gutters and downpipes are fixed with stainless round headed self tappers and fascia and soffit boards with countersunk even if they are covered with trims. Whilst they can be soft pilot holes and tapping with conventional screw first, avoids shearing. Our satellite dish is on an outbuilding so to avoid that rusting and staining our render on the house. Ducting underground brings the cable into the house. All soil pipes underground as well as all other services. Earlier this week watched a Grand Designs (repeat) programme of a very expensive build close to the sea shore on the Isles of Wight. They had some expensive timber cladding but within months the staining around the nail fixings was really bad particularly around the bottom where the rain and salt ends up. It really spoilt the look. some say it added character but for how long until the nail has rusted so much that boards come loose?. Bad attention to detail on I think was a £3 mio build. We are close to the sea and examples all around me of bad staining on new builds within months from rusting fixings.

316 SS is more corrosion resistant than 304 which are the typical grades. A2 screws which are most readily available are 304. Don't think you will find better choice than here.
https://www.accu.co.uk/?msclkid=a0c1cd9e79d4137a13b1a8bcecd6038d&utm_source=bing&utm_medium=cpc&utm_campaign=Brand%20-%20Accu%20%5BUK%5D&utm_term=accu&utm_content=Accu%20-%20Phrase.

Yacht chandlers I guess will have choice of SS but never used them.

316 and 304 are American SAE ratings corresponding to ISO A4 and A2 ratings respectively. You'll see both used in practice. 316 is the marine grade that is more resistant to staining etc and can be more difficult to find. Marine chandlers should have them, but they tend to be more expensive than e.g. caravan shops or other places that might stock them.