Corrosıon
 

CORROSION TESTS

Corrosion can be described as occurring degradation in the physical properties of material as a result of environmental interaction. Examples of types of corrosion are as follows breakage a metal as a result of the hydrogen embrittlement or cracking a polymer a result of excessive exposure to sunlight. Summary, corrosion can cause the weakening of materials, material loss,  deterioration of physical properties. Corrosion tests are very important. Because materials are exposed to corrosive effects under the service conditions. For this reason, corrosion types and causes should be investigated.

Intergranular Corrosion Test

Intergranular Corrosion Test is performed by ASTM A262 standard. This corrosion type is localized along the grain boundaries and usually associated with segregation effects or specific phases (carbides, nitrides, etc.) precipitated on the grain boundaries. Specific precipitation phases can cause occuring zone of reduced corrosion resistance in the immediate vicinity. (ASTM A262: Standard Practices for Detecting Susceptibility to Intergranular Attack in Austenitic Stainless Steels). There are several typesof this test such as;

-Oxalic Acid Test (Oxalic Acid Etch)

-Ferric Sulfate - Sulfuric Acid Test (Streicher Test)
-Nitric Acid Test (Huey Test)

-Copper - Copper Sulfate - 16% sulfuric acid Test (Strauss Test)

-Copper - Copper Sulfate - 50% sulfuric acid Test

Pitting Corrosion Test

Pitting Corrosion Test is implemented by ASTM G48 standard.Determination of pits, extent of its effect and evaluating of pitting corrosion are in progress Pitting Corrosion Test. This test is important because it can provide estimation of remaining life of a metallic material in service conditions and select the most-pitting resistant materials for real-life conditions. (ASTM G48:Standard Test Methods for Pitting and Crevice Corrosion Resistance of Stainless Steels and Related Alloys by Use of Ferric Chloride Solution).

HIC Test (Hydrogen-Induced Cracking)
HIC test is implemented as per NACE TM0248-2003 standard. HIC test is performed for detection of hydrogen inducing cracks of pipeline and steel walls of pressure vessels due to occuring hydrogen absorption in aqueous sulfide corrosion. Test specimens is dropped a specific solution for a certain time at ambient temperature and pressure. Then the sample is taken from solution and made the necessary investigations. (NACE TM0284-2003: Standart Test Method-Evaluation of Pipeline and Pressure Vessel Steels for Resistance to Hydrogen-Induced Cracking).

SCC Test (Stress Corrosion Cracking)
SCC test is performed byASTM G36 - 94(2006) standard. Stress corrosion cracking is a failure mechanism that environmental conditions and tensile stresses be effective on the susceptible material. In addition, an important effect is temperature in the formation of cracks.
A partial crack should be located in the sample that promoted the environmental conditions for occuring this failure mechanism. In addition, the sample should be made susceptible material and should be exposed tensile stress over the threshold value. In some cases, the residual stresses in the material may be effective in the failure analysis without the need to apply a load. (ASTM G36 - 94(2006):Standard Practice for Evaluating Stress-Corrosion-Cracking Resistance of Metals and Alloys in a Boiling Magnesium Chloride Solution).

Salt Sprey Test
Salt Spray Test is performed byASTM B117 standard. Salt spray test is doneto test organic or inorganic coating and especially to determine the product specification. In this test, the uniformity of coating thickness, porosity amount in coatings, etc. can be determined. (ASTM B117 – 11:Standard Practice for Operating Salt Spray (Fog) Apparatus).