Corrosion, Failure Analysis and Materials Selection Specialists

 

 

 

 

 

Corrosion Testing / Failure Analysis

 

 

 

Corrosion Testing

Failure Analysis

Field Investigations

Litigation

Metallography

Technical Papers

CTL Profile

Pricing & Policies

Contact CTL

Quality Assurance

Electrochemistry

Heat Transfer Tests (Hot Wall Tests)

Immersion Tests

LABORATORY RESEARCH

 

DOT / EPA CORROSIVITY TESTS

Department of Transportation (DOT)
 

DOT requires a biological test and a metal test for non-corrosive classification. It must pass both to be certified as non-corrosive. If Packing Group I, II, or III has been established by the biological (skin) tests, then the metal tests are not required.

Title 49 CFR 173.136 a1 and 173.137 states that a liquid or solid will be assigned to Packin Group I, II, or III based on the time required to cause skin destruction of the back of six albino rabbits. Destruction within the first three minutes is Packing Group I, within one hour is Packing Group II, and within four hours is Packing Group III. Longer than four hours is considered Non-corrosive to skin (then the metal corrosion tests must be run). At CTL, we do not perform the rabbit testing.

As an alternate to using live rabbits, DOT has approved (exemption DOT E 10904) a synthetic biological test (synthetic skin) developed and patented by InVitro International, of Irvine CA. CTL uses the InVitro product.

Title 49 CFR 173.136 a2 & 173.137 c2 states that a liquid will be in Packing Group III if it corrodes 1020 steel or 7075 aluminum at a rate greater than 6.25 millimeters (mmpy). Both metals must be tested.

 

Environmental Protection Agency (EPA)

40 CFR Chapter I, Paragraph 261.22 (Characteristic of corrosivity). EPA Publication SW 846, Method 1110 (Corrosivity Toward Steel).

 

ELECTROCHEMISTRY

 
Corrosion is defined as a deterioration of a metal due to its reaction with the surrounding aqueous environment. This reaction is an electrochemical process, where at the anode there is oxidation of the metal to form a corrosion product (i.e., rust) and the release of electrons, and at the cathode there is reduction of dissolved ionic species (i.e., hydrogen or carbonates) and the consumption of electrons. This flow of electrons between the anode and the cathode can be measured by instrumentation (i.e., a potentiostat).
Several test procedures are available for evaluating the electrochemical behavior of a metal/solution reaction, they are:
 

Potentiostatic and Potentiodynamic Polarization, ASTM G 5
Potentiodynamic Polarization Resistance, ASTM G 59
Cyclic Potentiodynamic Polarization, ASTM G 61
Critical Pitting Temperature, ASTM G 150
Galvanic Corrosion
Rp/Ec Trend Analysis
Open Circuit Potential

 

HEAT TRANSFER TESTS (Hot Wall Tests)

 

This test is used to evaluate the condition where the metal vessel wall is hotter than the bulk solution. This condition is typical of an externally heated vessel.

The corrosion reaction is influenced by temperature. Generally, an increase in temperature signifies an increase in corrosion activity. Laboratory immersion tests conducted at the bulk solution temperature may indicate that an alloy is acceptable for vessel construction. However, when the externally heated vessel is put into service, higher corrosion activity may be observed. This is due to the elevated metal temperature which was not simulated in the standard immersion tests. The Hot Wall Test is a laboratory simulation of an externally heated vessel.

This test can be tailored to meet specific needs concerning temperature and pressure.

 

IMMERSION TESTS

 

Immersion testing is the simplest and most popular form of corrosion testing performed. Numerous ASTM, NACE, ISO, and MTI standards deal with procedures for performing immersion testing to evaluate various materials under specific conditions. Immersion testing is a very flexible method which can be tailored to meet the specific needs of an application.

Test apparatus can be configured to allow exposure of test specimens to various phases of the test solution (liquid, vapor, condensate, liquid/vapor interface, ).

The test specimen can be modified to simulate various metallurgical or physical conditions (heat treatment, stress, crevice, surface finish, coatings/linings, )

The test environment can be controlled through temperature, pressure, agitation, velocity, and/or purge gasses.

Some of our specialized test equipment is listed below:

Autoclaves - Teflon
Autoclaves - 316 SS (3000 psi)
High Temperature Tube Furnace (1000C)
High Temperature Crucible Furnace (1000C)
Flow Loop (135 gallon loop)
Velocity Tester
Proof Rings
Humidity Chamber

Site Index

Site Copyright 1995 - 2007, All Rights Reserved,

Corrosion Testing Laboratories, Inc.

60 Blue Hen Drive

Newark, Delaware USA 19713

Phone: 1-302-454-8200

Fax: 1-302-454-8204

web@corrosionlab.com