INDUSTRIAL WATER CORROSION

PRESENTED BY

YASER SALEEM SIDDIQUI

M.TECH – CIVIL(ENVIRONMENTAL ENGG.)

3RD SEMESTER

WHAT IS CORROSION?

• CORROSION MAY BE DEFINED AS THE GRADUAL DESTRUCTION OF MATERIALS

WHICH ARE USUALLY METALS DUE TO THEIR CONTACT WITH THE SURROUNDING

ENVIRONMENT.

• IT IS BASICALLY THE CHEMICAL OR ELECTROCHEMICAL DESTRUCTION OF METAL

WITH ENVIRONMENT.

• CORROSION DEGRADES THE METALS THEREBY REDUCING STRENGTH AND

OTHER PHYSICAL AND CHEMICAL PROPERTIES OF METAL.

SIGNIFICANCE OF THIS PRESENTATION

• AS FAR AS THE TOPIC OF THIS PRESENTATION IS CONCERNED,WE SHALL DISCUSS

THE PROBLEMS DUE TO CORROSION IN INDUSTRIAL WATER.

• CORROSION HAS VARIOUS EFFECTS ON INDUSTRIAL WATER SUPPLIES.

• THE MAIN PROBLEMS IN INDUSTRIAL WATER SYSTEMS ARE;

1.SCALING

2.CORROSION

3.MICROBIOLOGICAL CORROSION

4.DISPOSAL OF RESIDUAL WASTEWATER

5.BIOFOULING

SCALING:

• SCALING OCCURS WHEN THE TEMPERATURE AS WELL AS THE

CHEMICAL CONDITIONS ARE SUCH THAT THE DISSOLVED

MINERAL SALTS WHICH ARE PRESENT IN WATER PRECIPITATE

AND FORM SOLID DEPOSITS.

• SCALING REDUCES THE HEAT EXCHANGE EFFICIENCY AS IT

BECOMES AN INSULATING MEDIUM.

• SCALING CAUSES WASTAGE OF ENERGY.

• SCALING IS RESPONSIBLE FOR INCREASE IN PIPE

WIDTH(DIAMETER),WHICH INCREASES THE LOAD ON THE PUMP.

CORROSION:

• CORROSION OCCURS AS A RESULT OF OXIDATION OF

PARENTAL METALS SUCH AS IRON RUSTS.

• THE INTEGRITY OF THE VARIOUS PLANT EQUIPMENTS

IS THEN GRADUALLY COMPROMISED.

• CORROSION CAN BE RESPONSIBLE FOR CAUSING

LEAKS.

• LEAKAGES IN PRESSURISED SYSTEMS MAY BE VERY

DANGEROUS FOR THE PLANT WORKERS.

MICROBIOLOGICAL CORROSION:

• UNTREATED COOLING WATER IS WARM AND MAY CONTAIN

ORGANIC NUTRIENTS.

• MICROBES GENERALLY THRIVE IN SUCH WATERS AS THE WET

COOLING TOWERS ARE GOOD AIR SCRUBBERS.

• DUSTS, FUNGAL SPORES, GRASS,FLIES ETC. GET COLLECTED

IN THE WATER AND THEREBY FORM OF ‘MICROBIAL SOUP’ IF

THEY ARE NOT WELL TREATED WITH BIOCIDES.

• DEADLY LEGIONNAIRES' DISEASE IS ALSO CAUSED DUE TO

THE PROBLEM OF UNTREATED COOLING WATERS.

DISPOSAL OF RESIDUAL INDUSTRIAL WASTEWATERS:

• THIS IS ONE OF THE MOST DIFFICULT CHALLENGES WHICH HAS TO BE TACKLED.

• THIS IS DIFFICULT AS WELL AS COSTLY.

• MANY CHEMICAL, PETROCHEMICAL REFINERIES AND PLANTS HAVE AN ARRANGEMENT OF ONSITE DISPOSAL OF THEIR RESIDUAL WASTEWATERS.

• THE POLLUTANT CONCENTRATION LEVELS OR PERMISSIBLE LIMITS SHALL COMPLY WITH THE LOCAL/NATIONAL REGULATIONS AS FRAMED BY THE GOVERNMENT SO AS TO DISPOSE THE WASTEWATER INTO COMMUNITY TREATMENT PLANTS, RIVERS, LAKES OR SEAS.

BIOFOULING:

• IT IS A PHENOMENON WHERE WATER SURFACES IN CONTACT

WITH WATER ARE COLONISED BY MICROORGANISIMS.

• CORROSION ASSOCIATED WITH MICROORGANISIMS HAS BEEN

RECOGNISED FOR OVER 50 YEARS.

• BIOFOULING IS A CRITICAL ISSUE IN MEMBRANE WATER AS WELL

AS WASTEWATER TREATMENT.

• BIOFOULING GREATELY COMPROMISES THE EFFICIENCY OF

TREATMENT PROCESSES.

• MEMBRANE FOULING IS A MAJOR PROBLEM ENCOUNTERED IN

MEMBRANE FILTERATION PROCESSES.

• IT IS A MAJOR FACTOR IN DETERMINING THE PRACTICAL

APPLICATION IN WATER AND WASTEWATER TREATMENT AND

DESALINATION IN TERMS OF TECHNOLOGY AND ECONOMICS.

ADVERSE EFFECTS OF BIOFOULING:

• MEMBRANE FLUX DECLINE DUE TO FORMATION OF LOW PERMEABILITY BIOFILM

ON THE MEMBRANE SURFACE.

• INCREASED DIFFERENTIAL PRESSURE AND FEED PRESSURE BEING NEEDED TO

MAINTAIN THE SAME PRODUCTION RATE DUE TO BIOFILM RESISTANCE.

• MEMBRANE BIODEGRADATION CAUSED BYACIDIC BY-PRODUCTS WHICH ARE

CONCENTRATED AT THE MEMBRANE SURFACE.

CORROSION CONTROL TECHNIQUES:

• BASICALLY THERE ARE FOUR METHODS FOR CORROSION CONTROL

1.COATINGS AND LININGS.

2.CATHODIC PROTECTION(CP)

3.MATERIALS SELECTION.

4.CORROSION INHIBITORS.

• COATINGS AND LININGS ARE OFTEN APPLIED IN CONJUNCTION WITH CATHODIC PROTECTION SYSTEMS IN ORDER TO PROVIDE A COST-EFFECTIVE PROTECTION SYSTEM FOR A STRUCTURE.

• CATHODIC PROTECTION (CP) IS A TECHNIQUE THAT USES DIRECT ELECTRICAL CURRENT IN ORDER TO COUNTERACT THE NORMAL EXTERNAL CORROSION OF A STRUCTURE, THAT CONTAINS METAL SUCH AS AN UNDERGROUND PETROLEUM STORAGE TANK OR NATURAL GAS PIPELINE.

• MATERIAL SELECTION REFERS TO THE SELECTION AND USE OF CORROSION RESISTANT MATERIALS SUCH AS STAINLESS STEEL, PLASTICS AND SPECIAL ALLOYS TO INCREASE THE LIFE SPAN OF A STRUCTURE.

• CORROSION INHIBITORS ARE THE SUBSTANCES THAT WHEN ADDED TO A PARTICULAR ENVIRONMENT,DECREASE THE RATE OF ATTACK OF ENVIRONMENT ON THE MATERIAL SUCH AS METAL.THEY CAN HELP TO INCREASE THE LIFE SPAN OF A METAL USED AS PIPES OR IN ANY PART OF A STRUCTURE.

EPOXY COATING

SOME COMMONLY USED CORROSION INHIBITORS FOR VARIOUS PURPOSES

• THESE CORROSION INHIBITORS INCLUDE

1. ANODIC INHIBITORS

2. CATHODIC INHIBITORS

3. BOTH (FILMING AMINES, PHOSPHATES)

SCALE/DEPOSIT CONTROLLERS:

• CONGLOMERATION OF MANY CONSTITUENTS THAT CAN RANGE FROM SETTLED SOLT FROM AIR BORNE DUST BLOWN INTO THE COOLING TOWER TO PRECIPITATE.

1.PHOSPHATES

2.PHOSPHONO-CARBOXYLATES

3.ORGANIC ACIDS

4.POLYMERS

COOLING WATER SYSTEMS:

• A COOLING SYSTEM IN WHICH WATER IS USED AS A COOLING AGENT TO

PROVIDE COOLING ACTION AND THEREBY LOWER THE TEMPERATURE.

TYPES OF COOLING WATER SYSTEMS:

• THE WATER CAN BE DISCHARGED AT THE INCREASED TEMPERATURE INTO A

RECEIVING BODY ONCE THROUGH COOLING SYSTEM OR IT CAN BE COOLED AND

REUSED(RECIRCULATING COOLING SYSTEM)

• THERE ARE TWO TYPES OF COOLING SYSTEMS NAMELY;

1. OPEN SYSTEMS

2. CLOSED RECIRCULATING SYSTEMS

• IN OPEN SYSTEMS COOLING IS ACHIEVED THROUGH EVAPORATION OF A FRACTION

OF THE WATER. EVAPORATION RESULTS IN LOSS OF PURE WATER FROM THE SYSTEM

AND A CONCENTRATION OF REMAINING DISSOLVED. WATER MUST BE REMOVED OR

BLOWN DOWN IN ORDER TO CONTROL THIS CONCENTRATION AND FRESH WATER

MUST BE ADDED TO REPLENISH THE SYSTEM.

• IN CLOSED RECIRCULATING SYSTEMS, THERE IS A COOLING SYSTEM WITHIN A

COOLING SYSTEM. THE WATER CONTAINING HEAT TRANSFERRED FROM THE

PROCESS IS COOLED FOR REUSE BYMEANS OF AN EXCHANGE WITH ANOTHER FLUID.

WATER LOSSES ARE USUALLY SMALL.