Protection of cultural heritage by real-time corrosion monitoring

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AirCorr logger

Survey

AirCorr logger

The goal of the MUSECORR project is to develop electronic loggers for continuous measurement of air corrosivity. These loggers will be called AirCorr. Based on the results obtained in the survey of professionals working with cultural heritage objects, three versions of the AirCorr logger have been designed for specific applications:


AirCorr I: Indoor version with an exchangeable sensor	AirCorr I Plus: Indoor version with temperature and RH sensors, 2 exchangeable corrosion sensors, LCD showing actual corrosivity	AirCorr O: Watertight outdoor version

Main advantages of AirCorr

In 2010, prototypes of AirCorr loggers were developed and the first tests carried out. The main advantages of AirCorr are as follows:

Due to the great precision of the electronic device and the geometry of the metal track, both a quick response time and a highly sensitive measurement are achieved.
A wide range of sensors, including ultra-sensitive ones for low-corrosivity environments, is available to simulate most metals of practical interest.
The logger is small and can be placed virtually anywhere.
The metal sensors are easily replaceable thus reducing the operational costs.
Non-contact data reading allows the logger to remain in place while also allowing measurements to be monitored. In addition, optional remote data access is available.
The unit is designed to be autonomous for five years.
User-friendly software allowing for rapid interpretation of results and incorporating existing and proposed standards and recommendations is under development.

list of sensor materials and applications

AirCorr sensors

Sensor materials and approximate thicknesses are listed in the table, which includes both finalized sensors and those still in development. The resolution varies from under 0.1 nm for the sensors developed for low-corrosivity indoor environments to 200 nm for the robust sensors designed for highly corrosive outdoor applications.

Laboratory tests have shown that the sensors provide corrosivity data comparable to those obtained by traditional coupon techniques in significantly shorter time.

Examples of measurements

Examples of measurements are seen below. Changes in corrosion depth were registered at relative humidities from 33% to 85% and temperatures from 20 to 30°C on a 500-nm copper sensor (left) and a 50-nm silver sensor (right).

It is evident that both sensors have sufficient resolution to allow for detection of changes in the air corrosivity within minutes. Due to the linear response, the measured corrosion depths could be extrapolated to 30 days, the length of exposure time called for in several standards.