What Does Corrosion Rate Mean?
Corrosion rate is the speed at which any metal in a specific
environment deteriorates. It also can be defined as the amount of
corrosion loss per year in thickness. The speed or rate of
deterioration depends on the environmental conditions and the type
and condition of the metal under reference.
Several pieces of data must be collected when calculating the
corrosion rate of any given metal. Required data includes:
Weight lost (the decrease in weight of the metal during the
period of reference).
Density of the metal.
Total surface area initially present.
Length of time taken.
Corrosion pedia Explains Corrosion Rate
Corrosion rate is best expressed in terms of thickness or weight loss
where the surface of the metal corrodes uniformly across the area
that has been exposed.
It is found by:
R = d/t expressed in µm/y but can also be expressed in terms of:
Weight loss g/m2
mg/dm2.day
oz/ft2
Among others.
The total amount of lost thickness in micrometers is: d = total. Loss
occurrence is t = time in years.
This rate may vary if the rate expressed by the function above is
used to compare corrosion rates for a period of time not less than
one year with rates calculated over short periods. This is because
the short time rates are prone to fluctuating environmental changes
from season to season and also from day to day.
This method involves the exposure of a weighed piece of test metal
or alloy to the specific environment for a specific time. This is
followed by thorough cleaning to remove the corrosion products and
then determining the weight of the lost metal due to corrosion.
The rate can also be calculated as follows:
R = KW/ (?AT)
Where K = constant
W = total weight lost
T = time taken for the loss of metal
A = the surface area of the exposed metal
? = the metal density in g/cm³
Corrosion of iron in an aqueous corrosion can be used to explain the
other method of determining corrosion rate. The iron plate is dipped
into an aqueous solution and the increase in the accumulating iron
ions is measured by a photometric method, Fe3+.
