landowner

landowner

Pensioner Pete
Full Member
Either my full stainless exhaust system has gone rusty or the lad I bought it off was telling lies, what do you think, could it be very old stainless or have I been had ?
 

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how old is it. Certainly doesn't look like stainless. although stanless can actually stain, it shouldn't look like that. Looks like mild steel to me.
 
Baloo said:
how old is it. Certainly doesn't look like stainless. although stanless can actually stain, it shouldn't look like that. Looks like mild steel to me.
Click to expand...
Took it down to good metal with sandpaper and it looks like mild steel but can't be sure, there was a lot of surface rust.:)
 
not sure but i remeber hearing something about stainless is too hard to take the heat and movement on the joints so a lesser grade stainless is used (pure would break with the expantion contraction on the joints ) but dont quote me. think it was the same with my series 2A back box i had many moons ago :D
 
The Rimmer Brothers 'stainless' sports exhaust on my Range Rover Classic looks the same as the one in the photo. It IS stainless, but a pretty poor grade. The only bits that's still shiny are the silencers and tailpipe.
 
a magnet should'nt stick too decent quality stainless , the poorer the quality of stainless the more you magnet will stick ..... do it slowly ....
 
The Mad Hat Man said:
not true, Drippy - good quality stainless can also be magnetic.
Click to expand...

is that true daft ??? never heard that before .... we've tried a million times to take low grade stainless fer export and we get caught every time , they just test it with a magnet .
 
Stainless steel is commonly regarded as non-magnetic. This is not strictly true and the real situation is rather more complicated. The degree of magnetic response or magnetic permeability is derived from the microstructure of the steel. A totally non-magnetic material has a magnetic permeability of 1. Austenitic structures are totally non-magnetic and so a 100% austenitic stainless steel would have a permeability of 1. In practice this is not achieved. There is always a small amount of ferrite and/or martensite in the steel and so permeability values are always above 1. Typical values for standard austenitic stainless steels can be in the order of 1.05 – 1.1.

It is possible for the magnetic permeability of austenitic steels to be changed during processing. For example, cold work and welding are liable to increase the amount of martensite and ferrite respectively in the steel. A familiar example is in a stainless steel sink where the flat drainer has little magnetic response whereas the pressed bowl has a higher response due to the formation of martensite particularly in the corners.

In practical terms, austenitic stainless steels are used for “non-magnetic” applications, for example magnetic resonance imaging (MRI). In these cases, it is often necessary to agree a maximum magnetic permeability between customer and supplier. It can be as low as 1.004.

Martensitic, ferritic, duplex and precipitation hardening steels are magnetic, irrespective of the "quality" of the end product.
 
that nearly made me dikslexic that did .... i'm goin to read it again ..... slowly...
 
The Mad Hat Man said:
Stainless steel is commonly regarded as non-magnetic. This is not strictly true and the real situation is rather more complicated. The degree of magnetic response or magnetic permeability is derived from the microstructure of the steel. A totally non-magnetic material has a magnetic permeability of 1. Austenitic structures are totally non-magnetic and so a 100% austenitic stainless steel would have a permeability of 1. In practice this is not achieved. There is always a small amount of ferrite and/or martensite in the steel and so permeability values are always above 1. Typical values for standard austenitic stainless steels can be in the order of 1.05 – 1.1.

It is possible for the magnetic permeability of austenitic steels to be changed during processing. For example, cold work and welding are liable to increase the amount of martensite and ferrite respectively in the steel. A familiar example is in a stainless steel sink where the flat drainer has little magnetic response whereas the pressed bowl has a higher response due to the formation of martensite particularly in the corners.

In practical terms, austenitic stainless steels are used for “non-magnetic” applications, for example magnetic resonance imaging (MRI). In these cases, it is often necessary to agree a maximum magnetic permeability between customer and supplier. It can be as low as 1.004.

Martensitic, ferritic, duplex and precipitation hardening steels are magnetic, irrespective of the "quality" of the end product.
Click to expand...


so would any of that above rust (underwater:D ) :D :D
 
I have a boat, and obviously as much as possible (limited by cost) use stainless steel fittings and nuts/bolts etc. I have learned that there are differing grades of stainless steel - for example '18/0' stainless steel does have magnetic attraction - but is used in less aggresive situations - the 18/0 means it has 18% chromium, but no nickel in it (the second number would be the nickel quantity) - it would be no use to me on a sea going boat, nor would it make a good exhaust I would say - but there are loads of types of stainless steel made - there are 5 main different types in fact with varying qualities.

For stainless steel nuts and bolts you will usually see A1 to A5 listed.
A1 (despite how "A1" seems) is not so good in agressive condtions (I don't use it on my boat for example),
A2 is much better and is the grade of nuts & bolts I use on my boat (A4 would be OK too as it has Molybedenum in it, but it is less commonly seen) and in places I've used A2 nuts & bolts on my Landy (though not on aluminium- rather than me explain it all see Galvanic and Corrosion Capatability Chart - Engineers Edge if you are interested).


As regards the magnet test - try this - if you have a stainless steel sink, put a magnet on the flat draining board - there will be likely no or a very weak attraction - now try the same thing on the curve at the edge or the curve where it goes over to the sink.... this will often be more magnetic, which is caused by the working of the metal altering the structure, so the magnet test is not really all that helpfull (especially with pipe or bent suyrfaces) as an indicator. Of course, if there is a massive attraction, it's probably worth a closer look!
A friend of mine works in a car accesory shop that sells amongst the other stuff big bore back boxes for boy racers - I've noticed that they are really poor quality, and are all from the far east. I'd be surprised to find a Landrover exhaust coming from a similar source though, even a pattern part.
 
Magnet sticks to all the pipes but not the box :(

Not good then, although the end if the tail pipe does look as though it has been shiney at some time.
 
I think you will find that 304 will stick, 303 is a little bit magnetic, 316 will not stick and the cheap **** you get from china, well say no more.
 
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