Page 419 - Challenges in Corrosion Costs Causes Consequences and Control(2015)

CORROSION AND ENVIRONMENTAL IMPLICATIONS 397

5.14 BIOMEDICAL ENGINEERING

Corrosion of prosthesis or other medical implants is an important subject matter as
fatigue and corrosion fatigue of artificial heart valves or hip joints can be fatal. A heart
valve suffers stress cycling at 60–100 cycles per minute, 24 h a day for many years.
Instances of fatigue failure of heart valves have been reported. A ball-and-socket hip
joint made from a combination of titanium and stainless steels experiences severe
mechanical loads during jogging or even when descending stairs. It is to be noted
that the working environment of the hip joint insert is a warm saline solution that
would stretch the insert to its limit. The implants that are supposed to last 20 years
had to be replaced after only two or three years. These two examples indicate the
seriousness with which corrosion impacts present medicine and how the effects are
far more serious to people than simply the monetary value.

5.15 THE DEFENSE INDUSTRY

Failure of military weapons in action because of corrosion failure is serious and may
be dealt with by reliability, a wider issue that arose from the needs of the defense
industry. There is an old saying that the kingdom may be lost for the sake of a nail in
a horse’s shoe. Cascading consequences from apparently trivial situations can some-
times lead to a serious event or an incident like a war.
Many defense systems are idle for years with the expectation that they will function
effectively when the need arises. It is not possible to check out the weapons for proper
function as in the case of a torpedo or missile without actually firing. The weapons
for war are complex systems manufactured with lightweight corrosion-prone alloys
operating in corrosive and widely variable atmospheres. Sometimes the unlikely com-
bination of circumstances results in a failure at the critical time as it happened to the
British ammunition in India.

5.16 CORROSION AND ENVIRONMENTAL IMPLICATIONS

Acid rain, the greenhouse effect, and the depletion of the ozone layer are some of
the consequences of environmental pollution. The change in social perspective has
led to international agreement and legislation with respect to environmental damage.
Control of corrosion is an integral part of the pressure because when properly imple-
mented, engineering systems can function efficiently for a longer duration with less
wastage of material and energy sources and minimum pollution.
It is interesting to note that in the United Kingdom, 1 ton of steel is converted
into oxide rust every 90 s. Apart from the wastage of metal, the energy required to
produce 1 ton of steel from iron ore is equal to the energy requirement of a fam-
ily for 3 months. The international opinion of the Exxon Valdez spillage in Alaska
and that of an aircraft accident did not prevent Braer oil tanker spillage. Pollution
is still allowed to happen because of the improper attitudes and lack of international
action.