What is the stock downpipe made of?

[andy10v]

What is the stock downpipe made of? Mild steel or stainless?

Wanting to add an 02 sensor and wan to know what kind of bung to get.

[madpugger]

Metal

[Big Lee M]

Rust most of them ha ha

[nip]

What is the stock downpipe made of? Mild steel or stainless?

Wanting to add an 02 sensor and wan to know what kind of bung to get.

I would say mild steel

[driftin jo]

I'm not sure of the grade of steel but it's not mild steel as they don't rust like mild steel would.
You can have one 15+ years old and wile the surface is rusty coloured it has not been
eaten it away at all.

It's probably one of the high temperature steel alloys, there are many mixes but you will be able to weld 304 bung to it no problem as I have seen it done on a standard downpipe.

[Error404]

Yeah it doesn't actually "rust" you get surface corrosion but it doesn't seem to pit the surface at all

[re2500]

I was surprised when he told me but Charlie at ProSpeed told me that the stock downpipe tubing is stainless!!

[driftin jo]

I was surprised when he told me but Charlie at ProSpeed told me that the stock downpipe tubing is stainless!!

Yes, it probably will be defined as stainless, most likely 400 series, magnetic and containing only
chromium, as opposed to 300 series (304 /316 etc) that contain chromium, nickel and molybdenum respectively. In a lot of 400 series you can get oxidisation on the surface as we see on our downpipes but due to passivation the chrome oxide prevents further diffusion of oxygen into the surface and thus prevents further oxidisation (true rust) occurring.

[urS6Tom]

Yes, it probably will be defined as stainless, most likely 400 series, magnetic and containing only
chromium, as opposed to 300 series (304 /316 etc) that contain chromium, nickel and molybdenum respectively. In a lot of 400 series you can get oxidisation on the surface as we see on our downpipes but due to passivation the chrome oxide prevents further diffusion of oxygen into the surface and thus prevents further oxidisation (true rust) occurring.

Awesome knowledge

[andy10v]

Great, thanks for all the help guys, I will get a stainless bung, will normal stainless mig welding wire be ok for this?

[caterpillar]

its not a prob to weld, with autorepair wire, or 316 wire...the mild steel wire will rust alittle, but not cruisal...

[Error404]

I'm about to gut the pre-cats and move the 2nd lambda bosses on the Mrs' S4 downpipes, ok to use 304 MIG wire on this stuff?

[driftin jo]

yes, it will be fine

[Error404]

Thanks mate