Does Stainless Steel Corrode?

[halsey02]

"Sabotage not ruled out: SBS Transit on NEL disruption, Addressing the media in a press conference on Thursday evening, SBS Transit’s executive vice president for rail Wong Wai Keong said the main fault was caused by two stainless steel wires that were discovered to have snapped at 5am, which provided support to the electrical system powering the NEL trains.

He said that this was the first time such an incident (where the stainless steel wires snapped) had ever happened, adding, in fact, that they were “expected to outlast the system”.

“This is something that we are still investigating, because (the) two cables are actually stainless steel cables, which are supposed to be very strong,” he said. “And we have looked at the failed cables, the condition of the cable was in a good condition. There was no corrosion, there was nothing bad identified at the moment.”
(quote)

I did a google for stainless steel corrosion, the answer:

"In metallurgy, stainless steel, also known as inox steel or inox from French "inoxydable", is defined as a steel alloy with a minimum of 10.5[1] or 11% chromium content by mass. Stainless steel does not corrode, rust or stain with water as ordinary steel does, but despite the name it is not fully stain-proof.It is also called corrosion-resistant steel or CRES when the alloy type and grade are not detailed, particularly in the aviation industry. There are different grades and surface finishes of stainless steel to suit the environment the alloy must endure. Stainless steel is used where both the properties of steel and resistance to corrosion are required"
quote , abridged from wipipedia.

I am not a metalurgist, nor familar with metals, I have forgotten my Physics which I had studied, does Stainless Steel corrode?, anyone out there can enlighten?

 

[groober2011]

Stainless steel has about 150 grades and it depends on the environment where it is being used. Yes, stainless steel can be stained and corrode in some cases.

 

[Bigfuck]

All steels corrode. Stainless steel as rustproof is a myth. It depends on the environmental conditions that it is in. If you scratch stainless steel put it by the sea you will know. If you dip it in strong acid, you will know. Rusting is due to oxidation. If you put normal steel in de-oxygenated water for weeks, it will not rust. Put stainless steel in sea water for a few weeks, and you know. Some people in Singapore claiming to be qualified whatever, use low grade galvanized steel and claim that the structure can withstand sea water and sea breeze. These same types of whatever use second hand mild steel with compromised strength to construct live load structures deemed to be temporary. BTW, there are many grades of steels which are not what they are claimed to be when tested, especially from China.

 

[Bigfuck]

http://www.dieselduck.ca/machine/04 auxiliary/corrosion.htm
Coffee and donuts entertainment.
The only metal to our written civilization is Adamantium which is almost indestructible but has yet to be discovered by our scientists. It has already been harnessed by other great scientists who have crafted it onto Wolverines bones and skeleton. Perhaps, Mjolnir made from uru may destroy Adamantium in its secondary form.

 

[groober2011]

Here is a good explanation and will answer your question.

Corrosion mechanisms in stainless steel

Introduction

Stainless steels are generally very corrosion resistant and will perform satisfactorily in most environments. The limit of corrosion resistance of a given stainless steel depends on its constituent elements which means that each grade has a slightly different response when exposed to a corrosive environment. Care is therefore needed to select the most appropriate grade of stainless steel for a given application. As well as careful material grade selection, good detailing and workmanship can significantly reduce the likelihood of staining and corrosion.
Pitting corrosion

Pitting is a localised form of corrosion which can occur as a result of exposure to specific environments, most notably those containing chlorides. In most structural applications, the extent of pitting is likely to be superficial and the reduction in section of a component is negligible. However, corrosion products can stain architectural features. A less tolerant view of pitting should be adopted for services such as ducts, piping and containment structures. If there is a known pitting hazard, then a molybdenum bearing stainless steel will be required.

Crevice corrosion

Crevice corrosion is a localised form of attack which is initiated by the extremely low availability of oxygen in a crevice. It is only likely to be a problem in stagnant solutions where a build-up of chlorides can occur. The severity of crevice corrosion is very dependent on the geometry of the crevice; the narrower (around 25 micro-metres) and deeper the crevice, the more severe the corrosion. Crevices typically occur between nuts and washers or around the thread of a screw or the shank of a bolt. Crevices can also occur in welds which fail to penetrate and under deposits on the steel surface.

Bimetallic (galvanic) corrosion

Bimetallic (galvanic) corrosion may occur when dissimilar metals are in contact in a common electrolyte (e.g. rain, condensation etc.). If current flows between the two, the less noble metal (the anode) corrodes at a faster rate than would have occurred if the metals were not in contact.
The rate of corrosion also depends on the relative areas of the metals in contact, the temperature and the composition of the electrolyte. In particular, the larger the area of the cathode in relation to that of the anode, the greater the rate of attack. Adverse area ratios are likely to occur with fasteners and at joints. Carbon steel bolts in stainless steel members should be avoided because the ratio of the area of the stainless steel to the carbon steel is large and the bolts will be subject to aggressive attack. Conversely, the rate of attack of a carbon steel member by a stainless steel bolt is much slower. It is usually helpful to draw on previous experience in similar sites because dissimilar metals can often be safely coupled under conditions of occasional condensation or dampness with no adverse effects, especially when the conductivity of the electrolyte is low.
The prediction of these effects is difficult because the corrosion rate is determined by a number of complex issues. The use of potential tables ignores the presence of surface oxide films and the effects of area ratios and different solution (electrolyte) chemistry. Therefore, uninformed use of these tables may produce erroneous results. They should be used with care and only for initial assessment.
Austenitic stainless steels usually form the cathode in a bimetallic couple and therefore do not suffer corrosion. Contact between austenitic stainless steels and zinc or aluminium may result in some additional corrosion of the latter two metals. This is unlikely to be significant structurally, but the resulting white/grey powder may be deemed unsightly. Bimetallic corrosion may be prevented by excluding water from the detail (e.g. by painting or taping over the assembled joint) or isolating the metals from each other (e.g. by painting the contact surfaces of the dissimilar metals). Isolation around bolted connections can be achieved by non-conductive plastic or rubber gaskets and nylon or teflon washers and bushes. This system is a time consuming detail to make on site and it is not possible to provide the necessary level of site inspection to check that all the washers and sleeves have been installed properly.
The general behaviour of metals in bimetallic contact in rural, urban, industrial and coastal environments is fully documented in PD 6484 'Commentary on corrosion at bimetallic contacts and its alleviation'.

Stress corrosion cracking (SCC)

The development of stress corrosion cracking (SCC) requires the simultaneous presence of tensile stresses and specific environmental factors. It is uncommon in normal building atmospheres. The stresses do not need to be very high in relation to the proof stress of the material and may be due to loading and/or residual effects from manufacturing processes such as welding or bending. Caution should be exercised when stainless steel members containing high residual stresses (e.g. due to cold working) are used in chloride rich environments (e.g. swimming pools enclosures, marine, offshore).
General (uniform) corrosion

General corrosion is much less severe in stainless steel than in other steels. It only occurs when the stainless steel is at a pH value < 1.0. Reference should be made to tables in manufacturers' literature, or the advice of a corrosion engineer should be sought, if the stainless steel is to come into contact with chemicals.

Intergranular attack and weld decay

When austenitic stainless steels are subject to prolonged heating between 450-850[SUP]0[/SUP] C, the carbon in the steel diffuses to the grain boundaries and precipitates chromium carbide. This removes chromium from the solid solution and leaves a lower chromium content adjacent to the grain boundaries. Steels in this condition are termed 'sensitised'. The grain boundaries become prone to preferential attack on subsequent exposure to a corrosive environment. This phenomenon is known as weld decay when it occurs in the heat affected zone of a weldment.

Grades of stainless steel which have a low carbon content (~0.03%) will not become sensitised, even for plate thicknesses up to 20 mm when welded by arc processes (giving rapid heating and cooling). Furthermore, modern steelmaking processes mean that a carbon content of 0.05% or less is generally achieved in the standard carbon grades 304 and 316, so these grades will not be prone to weld decay when welded by arc processes.

http://www.bssa.org.uk/topics.php?article=95

 

[johnny333]

Terrorism It's amazing that people here seems to knows more about this then our scholars

I think the primary consideration at SMRT was cost. They simply cut too many corners Someone should ask that cheapskate ex-CEO how much was spent on maintenance vs on bonuses

 

[Bigfuck]

Terrorism It's amazing that people here seems to knows more about this then our scholars

I think the primary consideration at SMRT was cost. They simply cut too many corners Someone should ask that cheapskate ex-CEO how much was spent on maintenance vs on bonuses

Wah lao, blow below the belt in the groin even though absolutely correct. Kick some more Never forget
Wee Shu min - she inspires the best in us.

 

[Wildfire]

I've posted this in the other forum under "Politcal Issues" ... this is a repeat!

All these loose talks of possible "Sabotage" is just a way to divert public attention from the real culprits and buy time ... hopeful, the public will forget the incident after sometime!

"The cables are "supposed to be very strong" and a preliminary study showed that they were in good condition and did not show signs of corrosion," said Mr Wong.

My questions are:-
1. Have you not heard of metal fatigue or manufacturing defects?
2. I am surprised that you can tell so much from the "preliminary study" yet you can't tell whether the snapped ends look like a natural snap, sawed, sheared or pinched (as in using a wire cutter in the case of sabotage)?

So what is the real purpose of throwing up the word "sabotage" at such an early stage of "Visual Inspection" ... when the actual investigation has not even started!

Maybe, it is even an "Act of God" ... Let's move on!

 

[sta1100]

We know, from PRC all/everthing can, but problem is your problem when you buy from them.

 

[Unrepented]

My guess: metal, moisture, electric current, frequency, type of metal and grade, quality of metal and manufacturing process; the wrong metallic component gave way due to mixture of aforesaid factors.

Sabotage? Please show picture lah

 

[kingrant]

Agree with wildfire. Stress fatigue is a possibility. The stress level may be low but over millions of cycles, even SS can break. This Mr Wong sounds like an idiot.

 

[Loofydralb]

This is typical of cheebye management. Even before anything is confirmed, the cheebye mouth already talk about sabotage.

If I were one of the employees, tmr I throw my resignation letter to the cheebye management face. Want to anyhow accuse to cover their incompetencies?

 

[lianbeng]

"... Stainless steel does not corrode, rust or stain with water as ordinary steel does, but despite the name it is not fully stain-proof.It is also called corrosion-resistant steel or CRES when the alloy type and grade are not detailed, particularly in the aviation industry. There are different grades and surface finishes of stainless steel to suit the environment the alloy must endure. Stainless steel is used where both the properties of steel and resistance to corrosion are required"

lianbeng noted "...with water..." try concentrated hydrochloric acid?

 

[Bigfuck]

lianbeng noted "...with water..." try concentrated hydrochloric acid?

http://www.cip.ukcentre.com/rust2.htm
For your rusting pleasure.

 

[Agoraphobic]

"Sabotage not ruled out: SBS Transit on NEL disruption, Addressing the media in a press conference on Thursday evening, SBS Transit’s executive vice president for rail Wong Wai Keong said the main fault was caused by two stainless steel wires that were discovered to have snapped at 5am, which provided support to the electrical system powering the NEL trains. .........................

Time to dig out their records and check on the contractor - Shoddy workmanship?

Cheers!

 

[Kuailan]

Very simple when lowest tender gets the job what you expect from contractors? they also cut corners,
get the lowest metal & meterial available, and cheapest labour force, every thing thats cheap!

 

[po2wq]

This is typical of cheebye management. Even before anything is confirmed, the cheebye mouth already talk about sabotage ...

ya, man! ...

lidat anyhow say, anybody oso can anyhow say ...

mayb got hansum salesman or chiobu saleswoman involved ... like dat recent hi profile case lidat ... otherwise y managemen y so gan cheong quikly jump 2 conclusion n point fingers @ others ...

 

[Seee3]

....SBS Transit’s executive vice president for rail Wong Wai Keong .......

“This is something that we are still investigating, because (the) two cables are actually stainless steel cables, which are supposed to be very strong,” he said. “And we have looked at the failed cables, the condition of the cable was in a good condition. There was no corrosion, there was nothing bad identified at the moment.”

Quite surprised by the above comment. It is common knowledge to anybody dealing in underground structure to pay special attention to Corrosion especially when there is electrical cables nearby as the current will speed up corrosion. It is also common knowledge to engineer that there is such a thing called stressed corrosion and stainless steel is most susceptible to it. He should also know that a failure due to stress corrosion may not leave any stain behind. Lastly, he need to find out more about stainless steel as it may not be the best material against corrosion for underground structures especially with electrical current flowing in the vicinity. So sad, why didn't they learn from others or have they been conned?.

 

[qwerty]

cheated by contractors who use sub standard cables?

 

[johnny333]

cheated by contractors who use sub standard cables?

Lee-galised cheating maybe

I wouldn't be surprised if someone profited from the less stringent standards. Can ask anyone who's had to pay to replace their aluminum windows