Microbial Corrosion

Micro biologically-Influenced Corrosion (MIC), also known as microbial corrosion or biological corrosion is the deterioration of metals as a result of the metabolic activity of microorganisms.

There are about a dozen of bacteria known to cause micro biologically influenced corrosion of carbon steels, stainless steels, aluminum alloys and copper alloys in waters and soils with pH 4~9 and temperature 10oC~50oC.

These bacteria can be broadly classified as aerobic (requires oxygen to become active) or anaerobic (oxygen is toxic to the bacteria). Sulphate reducing bacteria (SRB) is anaerobic and is responsible for most instances of accelerated corrosion damages to ships and offshore steel structures. Iron and manganese oxidizing bacteria are aerobic and are frequently associated with accelerated pitting attacks on stainless steels at welds.





Many industries are affected by MIC:
Chemical processing industries: stainless steel tanks, pipelines and flanged joints, particularly in welded areas after hydro testing with Natural River or well waters.
Nuclear power generation: carbon and stainless steel piping and tanks; copper-nickel, stainless, brass and aluminum bronze cooling water pipes and tubes, especially during construction, hydrotest, and outage periods.
Onshore and offshore oil and gas industries: mothballed and waterflood systems; oil and gas handling systems, particularly in those environments soured by sulfate reducing bacteria (SRB)-produced sulfides
Underground pipeline industry: water-saturated clay-type soils of near-neutral pH with decaying organic matter and a source of SRB.
Water treatment industry: heat exchangers and piping
Sewage handling and treatment industry: concrete and reinforced concrete structures
Highway maintenance industry: culvert piping
Aviation industry: aluminum integral wing tanks and fuel storage tanks
Metal working industry: increased wear from breakdown of machining oils and emulsions
Marine and shipping industry: accelerated damage to ships and barge


Micro biologically influenced corrosion is caused by specific genera of bacteria which feed on nutrients and other elements found in waters and soils. Sea water is a primary source of sulphate reducing bacteria (SRB). The biological activities modify the local chemistry (acid-producing) and render it more corrosive to the metals. For example, iron-oxidizing bacteria can perforate a 5mm thick 316 stainless steel tank in just over a month.


Micro biologically influenced corrosion, or microbial corrosion or biological corrosion can be prevented through a number of methods:
Regular mechanical cleaning if possible
Chemical treatment with biocides to control the population of bacteria
Complete drainage and dry-storage

Solid Waste Generation

It is not easy being GREEN…

Solid wastes generation includes all discards from houses, businesses, as well as wastes from manufacturing construction and environmental cleanups.

The characteristics, quantities, volume and composition of solid wastes generated may differ from one country to another and between urban and rural areas. It depends on the customs, climate, living condition and economic standard of the area.

Aesthetic, land use, health, water pollution, air pollution and economic considerations make proper storage, collection and disposal of solid wastes municipal and individual functions that must be taken seriously. Indiscriminate dumping of solid wastes and failure of the collection system in a populated community would soon cause many health problems.

Determination of the generation rate of solid waste is important to obtain data in order to determine waste volume and for subsequent solid waste management. Generation rate estimate the amount of waste created by residences or businesses over a certain amount of time (days, year etc).Waste generation includes all materials discarded whether or not they are later recycled or disposed in a landfill.

Waste Management is an essential service to be provided by the municipal and local government authorities. But what is required is putting in place a professional management system, adoption of latest available technologies and best practices so that there is no failure in this essential service delivery to our citizens. Here comes the role of private sector with investment preparedness to take this forward.

air pollution on buildings

Air pollutants are of major importance for the deterioration of many materials used in cultural monuments. Environmental destructive factors such as severe fluctuations in temperature and moisture and the seasonal changes in these two factors, fire… are not new; they have always existed and have had their destructive effect on the cultural heritage over the years. Relative humidity and air temperature have definite effects on the stability and strength of monuments. Relative humidity of a specific amount of air is defined as the ratio between the amount of moisture in a specific amount of air and the moisture required for saturation of the same amount at the same temperature. Though there are many reasons for degradation the principal reason may be attributed to air pollution. The air pollution in the form of acid rain may be chiefly responsible. The pollutants that are principally responsible for acid rain are sulphur dioxide and nitrogen dioxides. These two are emitted from the combustion of fossils fuels like coal and oil. The rapid industrialization has encouraged the quantity of these emissions. The information on materials damage due to air pollution is very scanty. However, the information on corrosive effects of acid precipitation on metals is available for a few cities.

In fact, all most all materials are affected by the deposition of acid, but the degree of damage or intensity may be varied. Some of them are more susceptible to the affect such are Carbon, Steel, Zinc, Nickel, Limestone, Marble, Paints and some plastics. Basically metallic materials are spoiled due to corrosion. Oxygen and moisture are the chief agents responsible for corrosion. Submerged structures like foundations and pipes will also be affected by acidified waters due to corrosion caused by acid attack.

The damage due to air pollution on materials is really a serious concern since the service life of buildings is remarkably reduced. It is true that the intensity of manmade pollutants on building degradation is more than the impact of natural pollutants. Most importantly the affects of soiling, degradation, corrosion and erosion caused by So2 are very much serious. The effect of air pollution on materials may be seen in terms of discoloration, material loss, structural failing and soiling. Both discoloration and structural failure due to air pollution on buildings may be insignificant and that may not involve huge coasts. But the effect of corrosion due to acidic deposition costs a lot. Especially the effect of sulphur dioxide and nitrogen dioxide emissions is very much significant. The effect of calcium sulphate has been very significant and may be continued for fairly long time. When calcium carbonate dissolves in sulphuric acid leads to the formation of calcium sulphate. The calcium sulphate when it falls on stone breaks the surface of the building blocks.

All most all heritage structures are built up with lime stone and calcareous stones which are most vulnerable to corrosion. Hence continuous renovation and retrofitting is a must to protect our heritage. The historic structures all around the world are affected by acid rain. Most of the studies for the long time focused on the effect of sulphur pollutants, later the interest was diverted to the effect of nitrogen residues on the structures.in fact the effect of acid deposition on material can be studies under two important heads The Taj Mahal, one of the Seven Wonders of the World, and India’s pride, greatest land mark is also being threatened from air and water pollution. Charminar, one of the greatest monuments in India, is being threatened by air pollution.The present contribution showed a general description on the current state of some of the historical structures. In fact the present situation of historical structures is at critical junction. It is necessary that the appropriate governments should initiate substantial measures to control the damage of structures. The awareness among the public is also important to stimulate the concerned authorities to initiate control and remedial measures.