Corrosion is a natural process through which refined metals are converted into more chemically stable forms such as oxides, hydroxides and/or sulfoxides. Huge amount of metals get wasted annually due to corrosion. Chemical and/or electrochemical reaction with the working environment is the gradual destruction of materials due to corrosion.
The well-known form of corrosion is Rusting. Rusting in iron to iron oxide is a well-known example of electrochemical corrosion. Metals reacting with oxygen and sulfur is known as electrochemical oxidation.
Corrosion not only occurs in metal but also in many other materials like polymers or ceramics. The process of corrosion in non-metallic materials is called “degradation”.

One of the significant reasons for low quality metals or materials is corrosion due to which useful properties like strength, appearance and permeability changes to gas or liquid.

Due to rusting of iron and steel, the estimated economic loss is of £700,000,000 every year. The annual direct cost of metallic corrosion worldwide is $2.2 Trillion USD, predominantly due to Steel Corrosion. Large contribution of this cost is by North America while that of US is $423 Billion.

The main reason for corrosion is exposure to moist air. Corrosion occurs when the surface is exposed, locally forming pits or cracks. It  occurs less uniformly and extends across a wide area while corroding the surface. This process is less visible and predictable.

SIGMA TEST & RESEARCH CENTRE offer periodic testing service through its specialized testing staff and experts which help in preventing corrosion, ensuring the quality check and increasing life span of metal by identifying signs of fatigue, pitting, cracking and rusting as well as other form of damages. Problems like measurement of remaining wall thickness in pipes, tubes, or tank that may be corroded on the inside surface remains predominantly an important issue in the power generation and petrochemical.

SIGMA TEST & RESEARCH CENTRE offer metal investigation i.e. where corrosion has already taken place during operation. This is beneficial to make preventive action for better corrosion resistance.

Testing Methods

1. ASTM B117:

In Sigma Test & Research Centre corrosion is detected by Salt Spray Test / Salt Fog – ASTM B117. It is widely used and internationally recognized method for evaluating coating under highly corrosive marine conditions. It also helps in comparing two or more material. Fast way to analyze the corrosion due to chloride chemical and salt water is Salt Spray test. To collect corrosion resistance data from non-coated and coated alloy is the main purpose of Salt Fog/Salt Spray Test. Being oldest, corrosion test has been widely used and thus it became a universal test. In this test, it is possible to test different type of materials like painted, bare sacrificial or noble coating.

2. HIC Testing:

Hydrogen Induced Cracking Test is performed to accurately determine and test the hydrogen induced cracking over exposed surface of metal. HIC testing apparatus meets requirements of ASTM / NACE Standard TM0284 and is suitable to test material as per requirements of NACE MR0175.

3. Coating Evaluation:

It is widely used in electronic, biomedical and many other industries dealing in metals based item. It is a treatment which provides corrosion resistance to prevent failure and corrosion,improve reliability, and increase life of the product. Experts with modern and latest technology will provide clear, accurate analysis and solution to the client in a wide range of metal industries.

4. Hydrogen Embrittlement:

If steel becomes brittle and fracture due to subsequent diffusion of hydrogen then hydrogen embrittlement method is used. Stress, environment are secondary reason for the diffusion. The main cause for the diffusion is material and chemical properties of the metal in which hydrogen is introduced on the surface of a metal and hydrogen atom is individually diffused through the metal.

5. Sensitization:

When stainless steel is improperly heated, it leads to excessive formation of chromium carbides at the grain boundaries then sensitization occur. Inter-granular attack (IGA) and inter-granular corrosion (IGC) are well-known forms of corrosion that results in sensitization.

6. Intergranual attack in austenitic stainless steel tested by ASTM A262

7. As per client/industry specification Solution at SIGMA TEST & RESEARCH CENTRE

Through specialized staff and expert, we provide solution

  • To identify the root cause of corrosion
  • Comparing and selecting appropriate material
  • Estimating life of the product / metal
  •  Salt Spray ranking assessment
  • Electrochemical evaluation of material and coating

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