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In-situ water layer thickness determination during accelerated corrosion testing

In-situ water layer thickness determination during accelerated corrosion testing

A collaboration of researchers at the University of Virginia, Sandia National Laboratories Albuquerque and Tohoku University Japan have recently published a paper that outlines the design, construction, and validation for in-situ water layer thickness determination during accelerated corrosion testing. In this work the Henniker HPT-100 was used to remove hydrocarbon contamination from the surface within the sensor in order to give a uniform for water layer, thereby creating an experimental system geometry that is directly comparable to the modelled geometry thickness determination.

Many metallic structures are subject to corrosive conditions such as salt spray. A salt spray test is a method of checking the corrosion resistance of materials or coatings. The water layer (WL) formed on the surface of the material during salt spray plays a great part in the rate of corrosion of the material. The paper advances the understanding of measuring the WL during the salt spray test.

“Plasma cleaning allowed for a uniform WL to form, creating an experimental system geometry that is directly comparable to the modelled geometry”

henniker plasma citation news droplet formation on the surface of plexiglass surface before plasma cleaning

Figure 1 . (b)Droplet formation on the surface of the plexiglass surface before plasma cleaning. (c) Water layer formation after plasma cleaning.

Figure 1 displays the difference of the WL on the surface of the plexiglass before and after plasma treatment, allowing for a uniform WL measurement.

Read the full abstract below

Design, construction, and validation for in-situ water layer thickness determination during accelerated corrosion testing

Received 23 April 2020, Revised 24 June 2020, Accepted 30 June 2020, Available online 17 July 2020 |


  • Creation of sensor for water layer determination, ranging from 0−5 mm, in salt spray testing environments
  • Water layers measured in continuous salt spray test similar to ASTM B117.
  • Angle of exposure in standards determines if thin-film regime is achieved influencing corrosion rate.
  • Severe angles of exposure (>20 degrees) cause quasi-periodic run-off of water moving from bulk to thin-film conditions.
  • Angle variability in ASTM B117 can influence the corrosion rate.


A sensor to determine water layer (WL) thickness, ranging from 0−5 mm, in salt-spray testing is presented. WL thickness is based on electrical resistivity and sensor design was guided by Finite Element Modeling with validation under known WL thicknesses. WLs were measured in continuous salt spray testing and angle of exposure played the largest role in thicknesses. At angles greater than 20˚ from vertical, semi-periodic run-off decreased WLs up to 80 %. Finally, the exposure angle determines if thin-film conditions are achieved, likely influencing corrosion rate and morphology. Allowances for sample angle in testing standards pose a potentially large source of variability.

To read the full paper click here

Or view our dedicated Plasma Cleaning page and our HPT-100 Model page for more details.


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