View Full Version : Does Carbon Steel rust?


TheBlueDragon
04-08-2005, 16:57
Hi people,
I just wanted to know, Does Carbon Steel rust?
________
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Annoni_mouse
04-08-2005, 17:33
Carbon steel does rust-only stainless steels offer guarentees from rusting(and some of them rust if of a lesser quality :( ).Treated carbon steels(plated,chemically blacked),do offer a small amount of rust protection,but theyre not as hardwearing as stainless steels.

Hope this helps:thumbsup:

depoix
04-08-2005, 19:12
Originally posted by Annoni_mouse
Carbon steel does rust-only stainless steels offer guarentees from rusting(and some of them rust if of a lesser quality :( ).Treated carbon steels(plated,chemically blacked),do offer a small amount of rust protection,but theyre not as hardwearing as stainless steels.

Hope this helps:thumbsup: yes it does it has to be cared for,oiled etc,but its far superior to stainless in keeping a sharp edge,it turns black after time if you dont oil it,but a quick wipe with emery cloth will bring it back to its shiny original self,i have a knife over 30 years old made of carbon,a couple of strokes on a steel and you could shave with it,

fnkysknky
04-08-2005, 19:52
As stated it does rust - plastering trowels are made from it and they rust if not taken care of properly.

Andy78
04-08-2005, 20:41
Carbon steel comes in many different forms. Some will oxidise very rapidly, where as some will take years. Stainless obviously varies loads too according to the alloying agents it has added to it and it what quantities. Most commonly added are Chromium, Vanadium, Molybdenum, Manganese etc. All bringing different properties to the alloy.

Grim
11-08-2005, 11:38
to be anal (i have a masters degree in materials engineering), all steels contain carbon, that is their definition... iron + carbon (+other elements usually) = steel!
Steels with high carbon tend to corrode much slower than low carbon steels, which might be a more useful answer ;)

nick2
11-08-2005, 11:41
I'm confused, why doesn't stainless steel go rusty ?

(I'm ashamed I don't know more about steel being from Sheffield)

ferret
11-08-2005, 11:48
Originally posted by Mainframe
Hi people,
I just wanted to know, Does Carbon Steel rust?

Yes, to confirm my experience. I have two favorite pocket knives, one is an Opinel made from carbon steel and the other from Laguiole which is stainless. While the Opinel blackens easily and loses its edge quickly it regains it with a couple of wipes on a steel. The Laguiole, although undoubtedly beautiful and has a hard-wearing edge, once lost it takes work to regain a good edge.
Wish there were still people who came round to do sharpening.

nick2
11-08-2005, 11:52
Originally posted by ferret
Wish there were still people who came round to do sharpening.

Go to Mortons on West Street (next to the tram stop), they do a brilliant job sharpening knives.

eddies32
11-08-2005, 12:40
Originally posted by nick2
I'm confused, why doesn't stainless steel go rusty ?

(I'm ashamed I don't know more about steel being from Sheffield)

The addition of chromium (> 12%) causes an inert film of chromic oxide to be formed over the metal surface preventing the formation of iron oxide (rust). They are only 'stainless' in enviroments that do not damage the passive film.

Grim
11-08-2005, 14:32
Originally posted by eddies32
The addition of chromium (> 12%) causes an inert film of chromic oxide to be formed over the metal surface preventing the formation of iron oxide (rust). They are only 'stainless' in enviroments that do not damage the passive film.

Spot on ;) I'd add the oxide film very thin, and is quite adherant due to an increase in volume of the metal to metal oxide causing a compressive stress in the oxide film. The oxide that forms on normal steels is slightly lower in volume, causing tensile stress, and therefore craacks form, allowing further corrosion. (the oxides are strong in compression, but not in tension).

I've probably gone somewhat ott on the explanation there ;)

nick2
11-08-2005, 14:39
So the film doesn't wear off if the metal is inside your body (I'm thinking of piercings or those rods they put in bones) ?

ferret
11-08-2005, 15:12
Originally posted by nick2
Go to Mortons on West Street (next to the tram stop), they do a brilliant job sharpening knives.

Cheers, I'll go and see them.

Walkerdylan
16-04-2009, 07:44
yes it does it has to be cared for,oiled etc,but its far superior to stainless in keeping a sharp edge,it turns black after time if you dont oil it,but a quick wipe with emery cloth will bring it back to its shiny original self,i have a knife over 30 years old made of carbon,a couple of strokes on a steel and you could shave with it,

is there a certain grain that works best if you use emery cloth?

Skink
16-04-2009, 09:20
So the film doesn't wear off if the metal is inside your body (I'm thinking of piercings or those rods they put in bones) ?

also having degree in materials and masters in corrosion science wanted to add a little here

the surface of a material is generally what affects how it interacts with its environment - so surface and environment are important

"carbon steel" will not rust without moisture - keep it dry it will stay shiny, keep out water with oil and it will stay shiny, paint it properly and it will stay shiny (under the paint)

Rust is a soft oxide that is not well adhered to the surface of the metal, so it keeps rusting away. Bare metal that is outside and subject to rubbing may appear not to be rusting but it will be (railway tracks are a good example of both these mechanisms)

Stainless steels have a highly adherent oxide coating, <12Chromium is a minimum but this will show rust marks with salts or organic acids (think cheap cutlery left in food). Decent cutlery will be 18%Cr and 8%Nickel (called 18 8 )and is much more corrosion resistant. Once you start adding Molybdenum you are talking industrial grade corrosion resistance.

The thermo dynamics of the film formation on stainless steels are such that if the surface is scratched the new surface will pretty much instantly be protected

In vitro corrosion (ie inside the body) is a complicated subject but the materials used for pearcings etc are at a minimum going to be 18 8 (hopefully). Where there is a high wear or strength need (eg joints) highly specialised stainless steels (with Mo and Cobalt etc) or titanium are used

hope that helps

depoix
16-04-2009, 09:53
is there a certain grain that works best if you use emery cloth?to be honest,i dont know,i just reached into the tool box found a piece of emery cloth and worked the blade with it from its back to it's edge,it came up almost as good as new and once resharpened and oiled it was back to being a great knife

BJan
16-04-2009, 18:25
also having degree in materials and masters in corrosion science wanted to add a little here

the surface of a material is generally what affects how it interacts with its environment - so surface and environment are important

"carbon steel" will not rust without moisture - keep it dry it will stay shiny, keep out water with oil and it will stay shiny, paint it properly and it will stay shiny (under the paint)

Rust is a soft oxide that is not well adhered to the surface of the metal, so it keeps rusting away. Bare metal that is outside and subject to rubbing may appear not to be rusting but it will be (railway tracks are a good example of both these mechanisms)

Stainless steels have a highly adherent oxide coating, <12Chromium is a minimum but this will show rust marks with salts or organic acids (think cheap cutlery left in food). Decent cutlery will be 18%Cr and 8%Nickel (called 18 8 )and is much more corrosion resistant. Once you start adding Molybdenum you are talking industrial grade corrosion resistance.

The thermo dynamics of the film formation on stainless steels are such that if the surface is scratched the new surface will pretty much instantly be protected

In vitro corrosion (ie inside the body) is a complicated subject but the materials used for pearcings etc are at a minimum going to be 18 8 (hopefully). Where there is a high wear or strength need (eg joints) highly specialised stainless steels (with Mo and Cobalt etc) or titanium are used

hope that helps

Reading that I feel incredibly stupid :hihi:

Under which conditions would stainless steel rust? Would heat influence it at all? Thanks

Skink
17-04-2009, 07:49
Reading that I feel incredibly stupid :hihi:

Under which conditions would stainless steel rust? Would heat influence it at all? Thanks

why should anyone feel stupid for not knowing something they werent taught/told ?

stainless steels dont generally "rust" - that is form a red iron oxide. As others have already said, they form a very stable passive surface because of the Chromium etc and if the surface is going to corrode it usually does so by local breakdown of that coating, that can then lead to pitting because whatever started the local breakdown sticks around. The environment need to be aggressive (eg stuff like Chlorides, Organic Acids or even worse Sulphides). Sometimes impurties in the steel will act to initiate the surface breakdown and pitting, but you still need a bad environment too

Heat accelerates wet corrosion, something like a 10 degree increase in temperature gives roughly a doubling of corrosion rate. If you mean high temperature corrosion then its going to have to get pretty hot (600+?)before the surface starts to be damaged and it will depend a lot on the type of stainless steel, but sorry I dont know for sure as thats not my field

Twiglet
17-04-2009, 08:41
So the film doesn't wear off if the metal is inside your body (I'm thinking of piercings or those rods they put in bones) ?

They are usually titanium :) (and if they are steel it's 'surgical' stainless steel')

Cyclone
17-04-2009, 09:14
The steels are given different hardness ratings as well, which presumably depends on their exact alloy. I had a knife stamped stainless 440 (I think the 440 is the hardness), unfortunately I lost it when I left my rucksack unzipped.

Skink
17-04-2009, 10:59
The steels are given different hardness ratings as well, which presumably depends on their exact alloy. I had a knife stamped stainless 440 (I think the 440 is the hardness), unfortunately I lost it when I left my rucksack unzipped.

Well . . . steel heat treatment is a little more complicated

Stainless steels come in roughly two types that are defined by the atomic structure.

Austenitic ones typically have high alloy content, low carbon content and exceptional corrosion resitance - but tend to be softer so less suited to high strength applications - they have a 300 designation for example 316L is one of the commonest here (this may not be true any more, this is the old BSI designation from a few years ago and many people are familair with it)

Ferritic ones (and the related Martensitic ones) are very strong but have more of a tendancy to corrosion - they also respond well to heat treatment so can be made much harder, with a consequent reduction in corrosion resistance. These are designated as 400 series

440 is a cutlery grade but somewhat different to a typical 18 8 in that it has little Nickel but quite a bit of Molybdenum and high carbon (MoC is an excellent hardening agent) - so it can be heat treated to be pretty darn hard. If memory serves me right it was/is popular in swords

Greybeard
17-04-2009, 11:41
A brief history of steel

http://www.tf.uni-kiel.de/matwis/amat/def_en/kap_5/advanced/t5_1_4.html

Harry O
17-04-2009, 19:43
The steels are given different hardness ratings as well, which presumably depends on their exact alloy. I had a knife stamped stainless 440 (I think the 440 is the hardness), unfortunately I lost it when I left my rucksack unzipped.

The hardness of metals is usually determined by Brinell (HB), Rockwell (HRC) or Vickers (HV) tests. If memory serves me right Brinell and Rockwell hardness determination is accomplished by a machine that presses a steel ball into the test sample which leaves a circular indentation, the depth of which results in a hardness value given on the machine. The Vickers test uses a pyramidal diamond that leaves a squarish impression. This indentation is then measured across the two diagonals through an eyepiece featuring movable blades. the two readings are then averaged and looked up on a chart to give the actual hardness. No doubt I will have cocked up slightly and will appreciate any posts that restore my memory to a pre-alchohol state.

m_gobara
17-04-2009, 20:03
actually all metals rust depending up on its environement

Grandad.Malky
17-04-2009, 20:14
Well . . . steel heat treatment is a little more complicated

Stainless steels come in roughly two types that are defined by the atomic structure.

Austenitic ones typically have high alloy content, low carbon content and exceptional corrosion resitance - but tend to be softer so less suited to high strength applications - they have a 300 designation for example 316L is one of the commonest here (this may not be true any more, this is the old BSI designation from a few years ago and many people are familair with it)

Ferritic ones (and the related Martensitic ones) are very strong but have more of a tendancy to corrosion - they also respond well to heat treatment so can be made much harder, with a consequent reduction in corrosion resistance. These are designated as 400 series

440 is a cutlery grade but somewhat different to a typical 18 8 in that it has little Nickel but quite a bit of Molybdenum and high carbon (MoC is an excellent hardening agent) - so it can be heat treated to be pretty darn hard. If memory serves me right it was/is popular in swords


Top answer :thumbsup: having worked with stainless for 30 years I can vouch for this answer although I would question the heat treating of Ferritics, I thought only Martensitics were really heat treatable.

Cyclone
18-04-2009, 01:03
actually all metals rust depending up on its environement

Technically only metal with iron content rusts, since rust is the oxidation of iron.

Grandad.Malky
18-04-2009, 11:03
Other metals undergo equivalent corrosion, but the resulting oxides are not commonly called rust.


Carbon steel rusts when exposed to air and moisture. This iron oxide film is active and accelerates corrosion by forming more iron oxide.

Stainless steels have sufficient amounts of chromium present so that a passive film of chromium oxide forms which prevents further surface corrosion and blocks corrosion from spreading into the metal's internal structure.

Gary S
14-09-2009, 15:37
This web sites pretty good showing information on carbon steels and their properties. Rusting, galling and scaling temperatures shown on specific carbon and stainless steel grades http://www.westyorkssteel.com

Gazza

Nodens
14-09-2009, 15:45
So that's a yes :hihi:

Johnsteel
25-07-2014, 13:26
carbon steel does rust-only stainless steels

barleycorn
25-07-2014, 14:04
carbon steel does rust-only stainless steels
I think we established that 9 years ago.

jb

tzijlstra
25-07-2014, 14:12
Yes, to confirm my experience. I have two favorite pocket knives, one is an Opinel made from carbon steel and the other from Laguiole which is stainless. While the Opinel blackens easily and loses its edge quickly it regains it with a couple of wipes on a steel. The Laguiole, although undoubtedly beautiful and has a hard-wearing edge, once lost it takes work to regain a good edge.
Wish there were still people who came round to do sharpening.

I have an Opinel! Awesome little knife, only a ten centimeter blade, but I've had it for over 20 years now and it is still as sharp as when I first got it.

It is getting black though, I considered putting it in some cola as I know that clears rust, but I am not sure the blackness is in fact rust?