CARBON STEEL ALLOY: 

Carbon steel instruments are identified for their hardness and capacity to hold sharp, cutting edges. They are extra sensitive than stainless steel instruments to chemicals, are sensitive to corrosion, and require special handling.

STAINLESS STEEL ALLOY: 

The main elements of stainless steel alloy include iron, chromium, and nickel. The substance of carbon in a stainless steel alloy is directly related to the alloy’s hardness and ability to hold a sharp, cutting edge. The increase of chromium enhances corrosion resistance, and nickel improves the mechanical qualities of the metal. The difficulties with stainless steel instruments are discoloration, the constant necessity of sharpening, and corrosion when presented to certain chemicals. Some tools are made with two kinds of stainless steel. One is solid and maintains a sharp edge; this is managed to make the cutting edge or tip. The other is more resistant to corrosion and is fixed or soldered to the first to form the handle. The carbon in the alloy, which is required for hardness and a sharp edge, is the culprit that causes corrosion or rusting. Tool manufacturers reduce surface corrosion by using two methods:

PASSIVATION: 

Passivation is a chemical method that produces a thin layer of chromium oxide on the surface of the instrument. That layer is transparent but tough, and it defends the underlying metal. After passivation, the tool is much less likely to corrode.

ELECTROPOLISHING: 

Electropolishing provides a smooth, highly polished finish. A deeply polished surface is less likely to corrode. Electropolishing is an active process for polishing complex shapes.

RESIN HANDLES: 

Some tools may have resin handles. Inside the copal is a full-length, steel internal core for continued strength and real feeling. The holders may have grooves and knurling to increase rotational direction and to provide a light (but secure) grasp. Resin tools and items require specific care. Division of Stainless Steel and Carbon Steel Instruments
Stainless steel and carbon steel instruments should be kept separate throughout the cleansing and sterilization process. If prepared together, the carbon steel instruments may create cross-corrosion on the stainless steel tools.
Carbon steel instruments should be completely dried before sterilization to prevent rusting or corrosion. The use of a protecting rust inhibitor solution is supported before sterilization. Problems of Instruments

CORROSION: 

Corrosion is a method in which a metal is changed to a metal oxide. A simple example is when the iron is changed to iron oxide or rust. Corrosion happens because metal oxide is the lower-energy form of metal. Corrosion is developed in a warm, wet environment, such as in the mouth or an autoclave.

TARNISH: 

Tarnish is a chemical or electrochemical attack on a metal surface. In many conditions, corrosion starts as a surface discoloration called tarnish. If the tarnish is a perpetual film, it will defend the metal from the environment (like paint on metal) and prevent corrosion. Several films on metals are transparent and unseen, but they may still preserve the surface from corrosion. If the film is not connected and the surface is not protected, corrosion may proceed, and loss of substance will occur.

PITTING: 

Pitting is produced by a chemical and electronic attack on surfaces. Pitting is localized corrosion, and it is restricted by: Flushing instruments thoroughly after use Avoiding long illness to chlorides and acids Avoiding soaps with high pH Not combining metals in ultrasonic cleaners

SPOTTING: 

Improper drying leaves mineral deposits that produce spots. To avert this, check the operation of the autoclave, and use chloride-free explications for sterilizing, disinfecting, rinsing, and cleaning.