CT Corrosion 4

[bimr]

Ed,

Have you seen the numerous reports of stainless steel from the tesla cyber truck owners. Here is one today:

https://www.torquenews.com/11826/tesla-cybertruck-becomes-extensively-corroded-after-exposed-magnet

This doesn't appear to me to be a good application for stainless steel for numerous reasons.

 

[EdStainless]

The magnets form very tight crevices which are the worst for causing corrosion.
They trapped road grime and moisture, and this is what you get.
Rail cars made of 200 SS have been in service for decades, so it isn't the material per se.
What he did caused this.

 

[bimr]

CT owners have been complaining for months about other corrosion problems as well:

https://www.cbsnews.com/news/tesla-cybertruck-rusting-complaints-from-owners/

Some of the CT Owners are wrapping the "trucks" in vinyl for $6k wrap.

https://www.torquenews.com/11826/te...stainless-steel-becomes-permanently-blemished

"Tesla uses 301 stainless which is a cheaper version of 304 stainless. 304 is what DeLorean initially used before switching to 316 for more corrosion resistance. It primary motivation is cost, and they'll be able to overcharge on the back end for brushing/restoring the stainless, Alex at YouTube/Legit Steet Cars has a series on what this process and the specialty tools look like."

What is the plastic that manufacturers wrap stainless steel with at the factory?

 

[TugboatEng]

The picture is fake.

 

[3DDave]

The photo is real. The video explanation is a lie. It is a printed vinyl wrap to make the truck appear corroded.

 

[bimr]

Okay that was a scam, but many others are complaining:

Here are some more pictures

https://www.cbsnews.com/news/tesla-cybertruck-rusting-complaints-from-owners/

 

[3DDave]

Supposedly "Ultra-Hard 30X Cold-Rolled stainless-steel" Others claim it is 301.

I expect it is a combination of not keeping carbon steel from contacting the panels during manufacture, not performing post-fabrication passivation, and surface contamination out in the wild causing rust nucleation spots.

Use a high quality paste wax, just like other vehicles require.

I like the idea that others tried and failed and, rather than figure would why the failed, Tesla would just do a similar thing on a large scale, expecting it to turn out differently.

No one buying these has any room to complain. They wanted a vehicle intended to be disruptive and they are finding out they are who is being disrupted. I have yet to see a single feature of this vehicle that isn't a disaster.

 

[TugboatEng]

Do not use wax. Waxes will cause crevice corrosion. Use an acidic cleaner. Citric acid works well. If you want something in consumer packaging, boat wash products are typically oxalic acid based.

The corroded CT pic is obviously fake because it follows the corrosion patterns of a painted vehicle. The corrosion is mostly on the top which is the result of UV wear of the paint. There is no paint on the CT. There is also no staining on the black trim around the wheel wells.

Please learn to recognize fake images.

 

[bimr]

Was just wondering if the stainless will corrode under the vinyl wrap.

 

[3DDave]

This isn't a fake image. It is a real image of a decorated vehicle. It is a real decoration applied to a real truck.

Can't corrode if it cannot stay wet. Wax won't create crevices. It won't protect them either. But oxalic acid can accumulate in crevices and really make a corroded mess.

 

[bimr]

Forget about the fake vinyl image as it has nothing to do with my original questions which haven't been answered.

Question 1. Is automotive body work a good application for stainless steel?

Question 2. Does the vinyl wrap help or make the issue worse?

Question 3. What is the difference between a vinyl wrap and the plastic sheeting on new stainless steel.

Question 4. My understanding is that an application varying from wet and dry is not a good application for stainless. Is that correct?

 

[TugboatEng]

3DDave, were there no fake images before Photoshop?

As for the questions:

#1 That depends on the alloy. It needs to be crevice corrosion resistant.

#2 The vinyl wrap makes it worse as it can cause crevice corrosion. There may be some issues related to chlorides in the wrap as well.

#3 The plastic sheeting on new stainless is intended to prevent scratches. The cosmetic wraps need to be more UV resistant than the shipping wraps.

#4 As the surface dries chlorides get concentrated which can worsen corrosion.

 

[3DDave]

3DDave, were there no fake images before Photoshop?

There were, but that hasn't anything to do with the origin of this thread.

Had the admonition been "Please learn to recognize fake stories," then that would be sensible to this thread and, come January, we would be saying Madame President.

 

[TugboatEng]

There is a lot to unwrap here, Dave. You know that the graphics are misleading yet you support the message because Kamala should be President? TDS in the wild.

 

[3DDave]

The vinyl wrap is intended to be misleading. The picture is real. The story about the wrap is a lie. Not sure what "message" you think I support.

 

[EdStainless]

The mantra with SS outdoors is to keep the surface clean.
Let it get rained on as often as possible.
SS has a good track record as body material in cars, commercial vehicles, and trains.
Yes, you will likely get corrosion under the edges of the wrap.
Crap gets trapped and cannot be washed out.
And soaps are not always good.
Most liquid soaps use NaCl as a viscosity modifier.
Many of them are 2-5% salt.

 

[WKTaylor]

Any 'stainless steel' with enough ferrous content... to attract and hold a magnet... has to have either a rogue/excessive ferrous content... or is NOT 300-series SStl... series which is virtually non-magnetic.

Hmmm... the last DeLorean SStl body car I saw on the road... just recently... was in beautiful condition. I seem to recall no significant body rusting or spot-weld rusting ever. What specific SStl alloy was DeLorean built from?

Of course... All of SpaceX Starship Heavy's seem to have SStl spot weld corrosion... all over.... after just a few days outside in the Texas gulf-coast salty air

I wonder if the SStl used on Tesla truck is same as SpaceX boosters...

Hmmm I wonder if corrosion [red rust] could be evolving from non-passivated spot-welded SStl bodies?

 

[TugboatEng]

There are some 300 series stainless steels that become magnetic after cold working.

Passivation doesn't solve all corrosion issues related to welding. Carbide precipitation is requires heat treatment.

 

[EdStainless]

Virtually all common 300 and 200 SS alloys will become profoundly magnetic when cold worked.
It has almost no effect on general corrosion resistance.
Welding is another issue.
The Cr depletion that goes with carbide formation is the issue with sensitization.
The low Cr areas will corrode easier.
There is also the delta ferrite that forms in welding.
This phase is less corrosion resistant.
Fixing this requires an anneal.
There is also the formation of surface oxides.
This also ties up Cr and leaves the underlying metal less corrosion resistant.
This requires pickling to fix.
Blasting, grinding, or passivation will not fix this.
Passivation will remove free Fe from the surface that is from forming, handling, or contact with tools.

 

[WKTaylor]

FYI 300 series magnetic properties.

I checked the AeroSpace Metals Handbook*, before throwing my statement 'very low magnetic [permeability] for 300-series SStl' up-against the wall...

ASMH volume number, alloys...
#1301 301, 302 SStl
#1302 303, 303se SStl
#1303 304, 304L SStl
#1307 316, 316L SStl
#1308 321 SStl
#1309 347 SStl

OK, OK... I did not check all of the 300 alloys... 305, 309, 310, 314, 317... DANG.... just the ones I work with all the time.

Most have very low permeability at low hardness.... and even cold-worked hardness. to hard... tho... means too brittle.

SOME cold-formed 3xx SStl [301, 302] can gain magnetic permeability... but not that much and rarely, since highly strained metals would likely be thermal stress relieved after severe forming, unless of course... that was too expensive a step. But, then, if not, the vehicle WOULD have different permeability all-over-it... with highly strained areas more corrosion prone [transforms to martensite]... but that is NOT what I am seeing.

For sure NDI is NOT possible/practical using Magnetic Particle. So... applying a durable finish over the passivated SStl... would likely have value-added [I'm sure Tesla was trying to avoid costs from extra finishes on the SStl].

SO... any ideas regarding DeLorean SStl alloy?