SUSCEPTIBLE TO CORROSION

 MILD STEEL AND LOW ALLOY STEELS ARE HIGHLY SUSCEPTIBLE TO REACTING WITH OXYGEN AND CAUSING RUST WITH ACCELERATED CORROSION OCCURRING IN COASTAL AND MARINE LOCATION


THE IRON CONTENT IN STEEL IS OXIDIZED IN THE PRESENCE OF MOISTURE AND OXYGEN.

                   Fe + 3O2 + 2H2O = 2Fe2O3H2O

     STEEL + OXYGEN + WATER = HYDRATED FERRIC OXIDE(RUST)

HOWEVER STEEL CORROSION REQUIRES SIMULTANEOUS PRESENCE OF WATER AND OXYGEN. IN THE ABSENCE OF EITHER , CORROSION DOES NOT OCCUR.

SO RUSTING IS AN ELECTROCHEMICAL PROCESS.


HOW IS STAINLESS STEEL DIFFERENT FROM MILD STEEL?

HOW DOES IT RESIST RUSTING?

STAINLESS STEEL HAS A THIN LAYER OF OXIDE (CHROMIUM OXIDE) ON IT'S SURFACE. THIS RENDERS THE SURFACE ELECTROCHEMICALLY PASSIVE. THIS OXIDE LAYER IS NOTHING BUT THE REACTION OF CHROMIUM WITH MOISTURE. STEEL MUST CONTAIN A MINIMUM OF 10.5% CHROMIUM TO FORM THIS PASSIVE LAYER. SO, STAINLESS STEEL UTENSILS ONLY GET STRONGER, MORE RESISTANT TO CORROSION AND A FIRMER OXIDE LAYER THE MORE THEY ARE EXPOSED TO WATER AND THE ATMOSPHERE.

OTHER METALS LIKE NICKEL , MANGANESE AND MOLYBDENUM ALSO ADD TO CORROSION RESISTANCE OF STEEL.


HOW IS MILD STEEL DIFFERENT FROM STAINLESS STEEL?

WHY IS IT PREFERRED FOR CONSTRUCTION?

 

MILD STEEL                                            STAINLESS STEEL

CARBON-SOFT             ALLOYING ELEMENT               CHROMIUM-HARD

MORE MALLEABLE            FABRICATION              HARD TO FABRICATE

CHEAPER                      COST                          EXPENSIVE


-Veronica

Comments

Post a Comment

Popular posts from this blog

Steel Erection, Fabrication and Hybrid construction -Blog 16

Image
This blog is about how the steel sections are transported to the site, the issues involved with transportation, erection and fabrication along with the onsite constrains. TRANSPORTATION: The steel sections have to transported from the manufacturing site to the fabrication site and this becomes a tough task due to their size. Often large pieces cannot be transported in a single part, they are split or divided and shipped as two separate pieces or even as one piece to avoid damage or scratches. Temporary connections are made on the pieces to avoid damage and to keep the parts in place during transportation.     These parts are not transported in normal vehicles but require long trail vehicles to fit their length and size which again becomes a difficult task to turn around the corners of the road and at junctions     FABRICATION & ON SITE CONSTRAINS: Fabrication of steel on sites which are along the main road or at the corner site is very hectic as there is very...
Read more

BLOG-16 FABRICATION, ERECTION AND HYBRID STRUCTURES

Image
  FABRICATION: The process of  steel fabrication  involves grinding, welding, cutting, bending, drilling, punching, burning or melting and other general crafting methods using various high-quality tools and CNC equipment. ERECTION LIFTING, POSITIONING AND PLACING OF STEEL MEMBERS IN A STRUCTURE  Once the member(s) are lifted and placed in the required place, with the help of temporary supports and equipment, they are fastened and fixed, depending on the nature of connection.  Erections may be achieved by two techniques such as MEWP(Mobile Elevating Work Platforms) by Mobile crane and Tower cranes. HYBRID STRUCTURES Hybrid structures are structures built with composite materials a combination of different materials with steel. A common  hybrid system  consists of hollow core slabs together with steel or cast-in-situ concrete frames                       EXAMPLE STEEL WITH TIMBER     I...
Read more

STEEL , ALLOYS AND THEIR COMPARISON

Image
BLOG- 8                                     STEEL , ALLOYS AND THEIR COMPARISON                                                               STEEL AND ALLOYS                                               An alloy is a blend consisting of metal and other elements. Alloys are generally made for achieving properties like greater strength or resistance to corrosion. Steel is an alloy of iron. It mainly consists of iron with some small amounts of carbon. Definition ALLOY :      A homogeneous mixture of a metal with other types of elements                       ...
Read more