5
The OnGuard Technology
Introduction
Metal strips have been used to quantify the effects of the atmosphere on similar metal surfaces for decades. Originally,
the analysis of the reactive metal strips relied on simply determining the weight gain due to atmospheric gases reacting
with the base metal. Later, more involved laboratory analyses gave some additional information on what compounds
made up the resulting corrosion film that collected on the metal strips.
While this is a good technique, it requires that the metal strips be placed in the environment from 30 to 90 days and can
only report the total corrosion that has occurred during the test period. Corrosion, however, is most often an isolated
event, and seldom occurs at an equal rate over the 30-to-90-day testing period. The method allows no way to pinpoint
when any of the corrosion occurred, or to determine the severity of any particular corrosion event. Likewise, it cannot
detect what dramatic atmospheric changes, such as wind, temperature and humidity, have had on the corrosive activity
within indoor environments.
It is important to take corrective action at the time these dangerous atmospheric shifts occur instead of after damage from
corrosion has taken place. Getting information “real-time” gives users this advantage.
The OnGuard 1000 was the first instrument to provide real-time monitoring of environmental corrosion that can affect the
reliability of industrial electronics, computers, and control equipment. The OnGuard 1000 has also been used extensively
in museums and archives to monitor the environmental conditions that could irreparably damage precious artwork,
artifacts and archives. The OnGuard 2000 and related models are patented, second-generation instruments that provide
the same basic capabilities as the OnGuard 1000, with significant improvements in user interface, accuracy, and
application flexibility. The OnGuard Smart implements the most desired features of the OnGuard 2000, 3000, 4000
adding pressure measurements and Wi-FI Ethernet communications. In addition, the OnGuard Smart is housed in an
attractive enclosure that can address a variety of markets.
The OnGuard provides real-time measurements of the amount of corrosion forming on copper and silver surfaces by
corrosive gases present in the local environment. It also measures the temperature and relative humidity of the
environment, both of which can affect the corrosion rate of these metals.
All of the OnGuard measurements for corrosion rates, temperature, and relative humidity can be related to the
International Society for Measurement and Control (ISA) Standard S71.04-2013: Environmental Conditions for Process
Measurement and Control Systems: Airborne Contaminants and ISA S71.01-1986: Environmental Conditions for Process
Measurement and Control Systems: Temperature and Humidity. The silver corrosion rate measured by the OnGuard is
reported in an environmental classification of the newly issued ISA Standard S71.04-2013. Similarly, the OnGuard
measurements can be related to various archive and museum standards being utilized around the world.
OnGuard Smart units are equipped with the standard sensor set (temperature/relative humidity, copper corrosion, silver
corrosion and pressure). The OnGuard is capable of logging the sensor measurements
in internal memory at user-
selectable intervals, and this information is downloadable to a personal computer for viewing, graphing or archiving.
