Talk:Cold welding

message: This might be worth considering alongside the article. The analytical section of Gravity Probe B is composed of polished quartz elements that stick together by molecular attraction between the two surfaces, owing to their flatness bringing them into close enough proximity for the effect to function. There are no welds, glues, screws, straps, clamps or bolts involved.  — Preceding unsigned comment added by 109.155.95.68 (talk) 21:38, 31 August 2012 (UTC)
thread_title: Gravity Probe B

message: I know ultrasonic welding can be categorized as a type of cold-welding.  Does anyone know if it is also a type of friction welding?  Thanks.    
Marylee23 (talk) 21:12, 16 April 2008 (UTC)
thread_title: ultrasonic welding

message: The physics textbook I have here (Cutnell and Johnson) says that static and kinetic friction are thought to be caused by cold welding.  I'm not comfortable enough of the fact to add the fact to the page without verification; any input?  --ScottAlanHill 04:22, 8 June 2006 (UTC)
replies: text: I was told this in an engineering class. Certainly it's not the only mechanism, but apparently it is one. —Ben FrantzDale 05:25, 8 June 2006 (UTC)
thread_title: Static and Kinetic Friction

message: Because no one else has created a section for this, I will.
Galling, to me, seems sufficiently similar to Cold Welding to be included in this article, even if, as Metal Eon pointed out, it has slightly different requirements. Player 03 (talk) 02:01, 19 May 2008 (UTC)
replies: text: Cold welding is NOT always desired. Its not a process, its an effect. --93.221.231.115 (talk) 08:36, 7 January 2018 (UTC)
thread_title:  Galling 

message: The unsourced (and preposterous) speculations about gold nuggets forming by cold welding of gold particles underwater in streams (under "Applications") will be removed in a few weeks if at least one bona fide scientific journal cite isn't added to support them. There are research articles out there that specifically contradict this idea, see the gold nugget article. Rep07 (talk) 20:13, 18 August 2012 (UTC)
thread_title:  Nugget formation speculations 

message: I think there should be a detailed process how Cold welding occurs.
Charon77 (talk) 09:57, 4 October 2013 (UTC)
thread_title:  Process? 

message: The root problems are:
1.  Quoting a non-subject matter expert as if he were a subject matter expert.
2.  Linking to an authoritative source material that contradicts what the article says.
The cold welding in space section of this Wikipedia article states.
:"However, in 2006, Henry Spencer stated that the phenomenon of spontaneous cold welding in outer space is "basically a myth", pointing out that "there are no documented cases of it actually occurring in orbit, except in experiments deliberately designed to provoke it (with susceptible materials, great care to avoid contamination, and deliberate mechanical removal of oxide layers, etc.)."
Henry Spenser is a well known computer programmer.  He's not a metallurgist or metallurgical engineer.  An off-hand quote from a non-expert with no first hand knowledge is not worthy of inclusion in an encyclopedic article.
Spenser seems to be referring to the idea that some theories state that cold welding should not easily occur in space.
The problem with those theories is that they're wrong -- they don't explain observations of what actually happens.
This wikipedia article continues:
:Three years following this 2006 post the European Space Agency published a peer reviewed paper detailing why cold welding is a significant issue that spacecraft designers need to carefully consider. The conclusions of this study can be found on page 25 of "Assessment of Cold Welding between Separable Contact Surfaces due to Impact and Fretting under Vacuum". The paper also cites a documented example from 1991 with the Galileo spacecraft high-gain antenna (see page 2; the technical source document from NASA regarding the Galileo spacecraft is also provided in a link here).[4][5]
Page 25 of the ESA report linked to (European Space Agency)clearly states that:
:"3.  It has been shown that the theoretical predictions are by no means comparable with experimental data.
:...
:6.In order to avoid cold welding, polymers or ceramics can be selected, but these materials may not be suitable for space hardware and mechanisms. Hence, metal–metal contacts often cannot be avoided. In that case, in order to reduce the risk of cold welding, the first strategy would be to use dissimilar alloy pairs, e.g. stainless steel versus hard steel (low adhesion is likely). The second strategy would be to apply coatings, although here the type of contact and the substrate material need to be well known.
:...
:8. Under fretting conditions, none of the investigated coatings on stainless steel (SS17-7PH) is able to prevent cold welding. Also MoS2 is not effective under fretting, and the lubrication is quickly lost. Hence, the best strategy must be to use different steels (maximum one of which should be austenitic). Hard coatings should not be used on hard steels.
:In contrast with steel, hard anodising of aluminium prevents adhesion under fretting conditions, but much loose debris is formed. A thick ‘Keronite’ coating (20 μm), which is based on a plasma-electrolytic oxidation (PEO) process, is not only resistant to fretting but also avoids debris formation. A test using an uncoated titanium pin against coated titanium discs did not provide a ‘general solution’. All thin coatings – solid lubricants and hard coatings – were destroyed in the fretting contact. The best combinations still showed medium adhesion after breakage of the coating. The combination titanium and low-adhesion steel also did not provide a solution. Further research will target thick coatings produced by PEO (Keronite)."
So clearly the ESA (subject matter experts) are saying cold welding does occur in space and is so difficult to avoid that compromises on materials need to be made.  It then lists a few things they tried that failed to provide a solution to prevent what the ESA considers to be cold welding.
So either remove the ESA footnote because the reference contradicts the claims of the article, or update the article to agree with the reference given.
I've updated the article to agree with the reference given.  
If you want to change it back, I don't have time to argue.  But know that you'll be changing it back to being incorrect.  
However, you could change it in a way that would be correct by doing this:
:(a) Explain that Wikipedia's definition of cold welding in space is not the definition used by subject matter experts like the ESA, and 
:(b) that the ESA has published an academic report explaining the difficulty in preventing what it considers to be cold welding in space.
The ESA report is currently footnote 4:
:A. Merstallinger; M. Sales; E. Semerad; B. D. Dunn (2009). Assessment of Cold Welding between Separable Contact Surfaces due to Impact and Fretting under Vacuum (ESA STM-279 November 2009). ESA Communication Production Office. p. 2. . Retrieved 24 February 2013.
What I quote above was retrieved from that article on 2014-07-12.
50.71.210.133 (talk) 00:16, 13 July 2014 (UTC)
thread_title:  SPACE: Article contradicts authoritative reference given.  Article quotes a non-subject matter expert.