Marks on Larch cladding when using stainless steel nails

[David R]

Hi Folks,

 

Can anyone help me shed some light on why these marks have appeared on my larch cladding? The marks appeared within a couple of hours, the larch is green and it was raining.

 

The nails are Firmahold 2.8 x 63 stainless collated being fired from a Dewalt 18V nail gun. 

 

I might understand if the nails were galvinised, but for the marks to appear so quickly is worrying. Where the timber I used was a not damp from the rain there are no marks.

 

Thanks in advance.

Edited November 8, 2021 by David R

[JohnMo]

May be worth getting a magnet and check if magnetic or not, stainless isn't magnetic.

[Conor]

I'd presume they could be caused but the filings that come from when the nails are fired? 

[Ian]

A4 stainless steel would be better than A2 in locations anywhere near the coast or industrial areas.

A4 vs A2: https://www.bolts.co.uk/guides-and-tips/heads-threads-and-finishes/difference-between-a2-and-a4-stainless-steel/

[Temp]

Might be worth drilling some holes in scrap to see if the marks form without nails in the holes?

[TonyT]

It’s not the prongs on the nail gun is it?

 

[David R]

Thanks for the quick replies folks.

 

The nails are slightly magnetic, when tested with a powerful magnet, from a good bit of googling I understand that this could be possible. Working 300 series stainless can make it slightly magnetic.

 

I am trying to eliminate the gun as the cause, it could be fragments or nozzle marks. I have deeply scratched a test piece of timber with the nozzle and fired other nail types to see it they will mark, still no signs of marking.

 

The stainless steel nails in the test piece have a distinctive tear stain forming, the galvinised nails are showing no marks yet. ( I will upload a photo )

 

I will drill some holes in the test piece and see it the show any staining in the morning. 

 

I know that green larch has a quite high acetic acid content this and a combination of steel fragments, could be the culprit. Surly I cant be the only person to have come across this issue.

 

 

[David R]

Johnmo

 

I have tried the magnet on some other stainless nails and they are not magnetic. You could be onto something.

 

Timco are sending a courier to pick the nails up so they can investigate the issue.

[Iceverge]

14 hours ago, David R said:

I am trying to eliminate the gun as the cause

 

Just hammer in a couple of nails manually to compare.

 

[David R]

On 09/11/2021 at 11:17, Iceverge said:

 

Just hammer in a couple of nails manually to compare.

 

Iceverge

 

I did this along with several other types of nails to see if I could get the staining happen again. The test piece got a bit busy with most of them showing some staining.  I tried again today with another piece of larch now none are showing staining!   Confused dot com.