Materials Blog
Rust is not corrosion! Print E-mail
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2048px-Antwerp_riverfront_april_2012

Yesterday morning, they botched it once again on Radio 2 - a Flemish broadcasting station - by associating a certain word with an incorrect meaning. It's true that the Van Dale - official dictionary of the Dutch language - turns a blind eye to this meaning, but from a technical point of view, it's not at all correct.

The occasion? The 'Boerentoren' (Farmers' Tower) – the pride of Antwerp - has been put in scaffolding for a while, in order to do repairs and to apply a system to it that will better protect the underlying steel structure against 'corrosion'. That's right, 'corrosion' is the correct term here, and not 'rust', as was implied for the umpteenth time. Of course, rust is the consequence of corrosion, but rust is not the same as corrosion.

Allow me to clarify: corrosion is the solution of a metal, for example in water. This mechanism could more or less be compared to the dissolution of table salt in water. When you pour table salt into a pot of water in quantities that stay under the so-called 'solubility limit' of salt in water, the salt will dissolve into its building blocks, sodium and chlorine ions. If the concentration of salt remains below the solubility limit of salt in water, you won't be able to see that there's salt in the water. What happens to table salt in water can also happen with metals: they dissolve. For example, in steel the iron atoms 'dissolve', which means that iron ions are released into the water. That is what we call 'corrosion'. However, as long as the solubility limit of those iron ions in water hasn't been reached, you won't be able to see what's happening. In other words, you can't see any rust yet, but that doesn't mean there's no corrosion, no loss of metal, no loss of strength, etc. Therefore, it is perfectly possible for corrosion to occur, even though you can't even see a speck of rust yet.

So, what's this thing called 'rust' then? Rust is what you get when you exceed the solubility limit of the iron ions in water. Let's go back to our table salt comparison. If you keep adding salt to the pot of water, at some point you will exceed the solubility limit of salt in water. From that moment on, any salt you add will be 'too much' for the solution, and the excess salt will no longer dissolve, but instead visibly precipitate on the bottom of the pot. A different analogy: when you have a pot of water in which the solubility limit of the salt has not yet been reached, but you start to boil the water, at a certain point the solubility limit will be exceeded: the loss of water will increase the concentration of salt. When the solubility limit is exceeded, the sodium and chlorine ions will be bound together again and result in the precipitation of sodium crystals. For steel, this means that when the solubility limit of iron ions in water is exceeded, the excess iron ions will precipitate by binding themselves to hydroxide ions or oxygen. This chemical compound will manifest itself onto the nearby zones that are already corroding. Rust is the chemical bond between iron ions and hydroxide ions or oxygen.

If we summarize the previous two paragraphs, we come to this conclusion: rust is not corrosion, but rather the consequence of corrosion.

But the thing that also grinds my gears, is that language should be used to clearly and correctly inform people. The manner in which dictionaries and the media use 'rust' and 'to rust', causes much confusion from a technical standpoint. Unfortunately, even many people in the industry are confused. Too many people in the industry still wait 'until they see rust' or 'until it starts to rust', before taking action. But in many cases, by then it's already too late. The process of corrosion - loss of metal - has already been doing damage for a long time.

 

Frans Vos

General Manager Materials Consult bvba

Visiting professor KU Leuven

 
10 years Zuckerberg … 10 years urge for information versus the urge for objectivity Print E-mail
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photo-online_communityLinkedin, facebook, twitter, ecademy and likewise social media have become commonplace in our modern society. Companies that are not yet active on these platforms will unavoidably run behind their competitors that have embraced social media in their marketing strategy and in their communication to customers and other stakeholders.

Also as to communication on quite technical matters, such as failure analyses of consumer goods or industrial installations, social media are gaining influence as platforms for discussion, sharing ideas and experience etc. On Linkedin alone there are several dozens of groups, closed or open to the public, that debate and stipulate on failure analysis in general, on specific types of failure or on failure of specific components in particular. Yet, what are the associated risks? Are all group participants sufficiently qualified to give an advise? If you launch a question in these groups, is it wise to assemble your own answer and plan of action based on advises that are usually quite short and sometimes even contradictory? The advises given in these groups should indeed be regarded with lots of caution. And what with the inevitable legal implications and liability issues for everyone concerned?

Read it NOW in “Sense and nonsense of social media in failure analysis”, temporarily FREE download (free untill March 26th 2014): http://elsarticle.com/1ejAE86

 

Authors:

Dr. ir. F.J.H. Vos, Founder and General Manager Materials Consult bvba

Sam Verbeke, Attorney at law, Partner at Nelissen Grade Lawyers, Leuven (B)

 
Materials science is a bridge Print E-mail
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Currently this blog is only available in Dutch

 
De schadelijder als hoeksteen van een betrouwbaar schade-onderzoek Print E-mail
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Materials Consult had de eer een lezing te mogen verzorgen op het Lassymposium 2012, een organisatie van het Nederlands Instituut voor Lastechniek en het Belgisch Instituut voor Lastechniek. Wij houden eraan beide instanties van harte te danken voor de uitnodiging.

Naar aanleiding van deze presentatie werden we eveneens uitgenodigd een publicatie te verzorgen in het vaktijdschrift "Lastechniek".

Een samenvatting van de presentatie en het artikel vind je hieronder. Het volledige artikel kan nu gratis worden gedownload.

 

De schadelijder als hoeksteen van een betrouwbaar schade-onderzoek.

Als rechtgeaard geïnteresseerde in de techniek zou u natuurlijk niets liever willen dan dat u tot op de bodem kon uitvissen waarom bepaalde van uw constructies, installaties of producten de gestelde kwaliteitseisen niet hebben gehaald. Zo zijn er bv. bij de corrosie van een laszone vele ‘mogelijke’ daders aan te wijzen. Was het een slechte las en zo ja, was het de procedure, het lasmateriaal, de lasser of nog iets anders? Wat te denken van een eventueel verkeerd gebruik? Of zat er misschien iets in het water? Vele mogelijk oorzaken, waarbij u vanzelfsprekend de waarheid en niets anders dan de waarheid wil achterhalen.

Het bepalen van de grondoorzaak (root cause) en de daarbij horende schade-analyses is gewoonlijk voer voor specialisten, maar die kunnen zelden iets uitrichten zonder uw assistentie. Op basis van concrete voorbeelden neemt onze zaakvoerder Frans Vos u mee op een reis doorheen de hinderpalen van het schade-onderzoek. En zoals u zal merken … enkele eenvoudige leefregels laten u snel toe om uzelf en uw bedrijf veel leed en veel euro’s te besparen.

Voor de trouwe lezers van onze blogs, hierbij alvast een tip van de sluier: Wist u dat u veel nuttige informatie al kan opzoeken voor dat de schade-onderzoeker aan haar of zijn werk begint? Enkele voorbeelden:

  • lasser_met_computer_-_open_vizierType materiaal, indien mogelijk met materiaalcertificaat
  • Constructietekening en -dossier, inclusief eventuele lasprocedures
  • Procesgegevens zoals temperatuur, druk, product in de installatie
  • Eventuele historische gegevens zoals inspectierapporten, datarecordings, ...
  • In geval van schadedossiers: Verslag van uw eigen visuele bevindingen en dito foto's enz.

Ook kan u op voorhand al zorgen dat alle schadestukken op een traceerbare wijze zijn geïdentificeerd en gelabeld. En tot slot verdient ook de behandeling van de schadestukken op zich de nodige aandacht: check hiervoor onze rubriek 'Goed begonnen is half gewonnen'.

 

Frans Vos

Zaakvoerder Materials Consult bvba

 

 
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