Corrosion mesurement techniques

[stats_student]

Hi guys i was wondering if there are methods available which allows one to measure corrosion that occurs in areas of materials where obvious defects exist like holes etc.

Instead of using the conventional methods which measure uniform corrosion?

Thank you in advance.

 

[Nidum]

There are very crude and very sophisticated methods .

At minimum the corroded area gets cleaned up and visually inspected and plate thickness measured . Quite common practice is to remove sample bolts from any badly corroded area and measure plate thickness through the hole .

There are more sophisticated methods using ultra sound but these are often difficult to use for complex assemblies .

At top end of the scale there is X-ray and radioactive source imaging .

 

[stats_student]

is there a specific name for these high end techniques? like are the categorized in under some search name?

thanks.

 

[stats_student]

oh and also could you add an explanation by removing sample bolts from a hole. Is what you are saying is that one places a bolt in a hole then let corrosion take place and then measure the bolt?

thanks again

 

[Nidum]

https://www.google.co.uk/search?q=x...QB#tbm=isch&q=Corrosion+detection+using+xrays

https://www.google.co.uk/search?q=C...AUQ_AUoAGoVChMI2KHlv6W6yAIVAs8aCh0C1gfX&dpr=1

 

[Nidum]

oh and also could you add an explanation by removing sample bolts from a hole. Is what you are saying is that one places a bolt in a hole then let corrosion take place and then measure the bolt?

No - Bolts are removed from areas which are already corroded so as to allow examination of the hole and assessment of plate thickness .

It may sound odd but holes are sometimes deliberately drilled in corroded boiler plates so that thickness of plates can be measured . Hole is then closed again with screwed plug .

 

[stats_student]

is there a name for the curde measurement technique Nidum?

 

[Nidum]

is there a name for the curde measurement technique Nidum?

I can't think of one general name . It comes under things like ships hull inspection , crane inspection , boiler inspection , bridge inspection etc .

Here's a link for bridges : https://www.google.co.uk/search?q=B...-8&oe=utf-8&gws_rd=cr&ei=vG4aVteqOMGsa9-FupgL

One for ships hulls : https://www.google.co.uk/search?q=c...-8&oe=utf-8&gws_rd=cr&ei=-W4aVoXSHciza_bZsegC

And one for boilers : https://www.google.co.uk/search?q=c...iza_bZsegC#q=corrosion+measurement+in+boilers

 

[Nidum]

Corrosion detection methods have become more sophisticated in all branches of engineering in the last few years . The older cruder methods are being phased out and the more advanced methods are coming into common use .

Note that corrosion measurement is no use unless there is some standard available to decide what level of corrosion is allowable .

 

[Astronuc]

is there a specific name for these high end techniques? like are the categorized in under some search name?

thanks.

One could look at "localized corrosion monitoring" or "in situ assessment", or "in situ corrosion monitoring" as part of a phrase or in conjunction with corrosion, measurement and/or inspection as key words. One could also look for NDE/NDT or non-destructive evaluation/testing methods.

There are different approaches based on the scale. One may monitor the corrosion environment, e.g., measuring the electrochemical potential, but that requires know about the environment at the local of interest, and for a large system, e.g., air craft, ship, marine structure, nuclear reactor, space craft, there are lots of places to inspect and lots of environments. Looking at hundreds or thousands of rivets or bolts, or other connection for crevice corrosion is time consuming and may be unfeasible. Looking into large structures, e.g., pressure vessels, piping, beams, reinforced concrete structures can be very challenging.

In the case of inspection, one has various tools, e.g., ultrasonics, eddy current, visual, various radiographic (X-ray, gamma-ray, neutron) techniques. The problem with radiography is that the usually one has to place a source and detector on opposite sides of the structure of interest.

Examples of acoustic emission

Monitoring the corroding environment in conjunction with a structural analysis is yet another approach. The objective is to identify the locations most susceptible to corrosion and to monitor specific sites.

One would find a number of articles in Corrosion Journal on in situ assessment or monitoring of pitting or crevice corrosion.
e.g., http://corrosionjournal.org/doi/abs/10.5006/1.3452399

Of course, laboratory conditions (which tend to be more controlled) are more ideal than field conditions.