In range of 4-10 corrosion rate is fairly independent of pH, but it increases rapidly when pH falls below 4.

Data acquisition systems effectively accumulate, format, record and display data transmitted by sensors. Modern data acquisition systems are called as Supervisory Control and Data Acquisition (SCADA) systems.

The process of applying zinc over steel is called ?galvanizing? and has been used to protect iron and steel from rusting for over two hundred years.

Electronic means include voltage, current, pulse duration, etc. The mechanical means of signal transmission include movement of a pen, indicator, float or cable. Pneumatic means include a detector or an amplifier.

Reduction of metal thickness leading to loss of mechanical strength and structural failure or breakdown. When metal is lost in localised zones so as to give a crack like structure, very considerable weakening may result from quite a small amount of metal loss.

Alloying metal to produce a more corrosion resistant alloy, e.g. stainless steel, in which ordinary steel is alloyed with chromium and nickel. Stainless steel is protected by an invisibly thin, naturally formed film of chromium sesquioxide Cr₂O₃.

Percent of saturation for dissolved oxygen analyser is 0 ? 99.9%. Two methods of calibration are: standard with automatic temperature, altitude and salinity compensation and or is Isolated with 4 ? 20 mA, digital serial output.

There are three categories of process variables. Instrumentation and automatic control allow continuous monitoring of process variables, rapid transfer of data to operator or manager.

There are or cathodic reactions and additives that suppress se reactions called cathodic inhibitors. They function by reducing available area for cathodic reaction. This is often achieved by precipitating an insoluble species onto cathodic sites. Zinc ions are used as cathodic inhibitors because of precipitation of Zn(OH)2 at cathodic sites as a consequence of localised high pH.

The mechanical means of signal transmission include movement of a pen, indicator, float or cable. Pneumatic means include a detector or an amplifier. Electronic means include voltage, current, pulse duration, etc.