Copper corrosion testing

Carbonyl sulfide reacts with chlorine forming phosgene (qv) and sulfur dichloride [10545-99-0] and with ammonia forming urea and ammonium sulfide [12135-76-1]. Carbonyl sulfide attacks metals, eg, copper, ia the presence of moisture and is thought to be iavolved ia atmospheric sulfur corrosion (27,28). Its presence ia propane gas at levels above a few ppm may cause the gas to fail the copper-corrosion test. 

Copper and copper-containing alloys are susceptible to attack by elemental sulfur and hydrogen sulfide as well as organically bound sulfur. Active or elemental sulfur and hydrogen sulfide gas can attack copper to form copper sulfide, a dark-brown to black compound. This can be seen through ASTM D-130 copper corrosion testing. 

Pybum, C. M., F. P. Cahill, and R. K. Lennox. 1978. Sulfur compound interactions on copper corrosion test in propane. Energy ProcessingICanada. March-April, pp. 60-64. 

ASTM D130 Copper corrosion test bomb j... 

In view of the wide use of copper in electrical equipment, it is essential to ensure that the oil does not corrode this metal. Noncorrosive or corrosive sulfur can be verified by any one of several test methods (ASTM D-130, ASTM D-849, ASTM D-4048, ASTM D-4636, IP 154) in which the oil is heated in the presence of a metallic copper strip for a specified time at a specified temperature after which the strip must be discolored. In addition, corrosiveness toward silver is becoming increasingly important, and a test method (IP 227) has been developed that is closely similar to the copper corrosion test. 

Water and Untreated Acid These contaminants maybe carried over from some processes. Total acid umber, TAN, and copper corrosion tests will indicate that these contaminants are present in the re-refined base oil. 

It is seen in Table IV that both pilot plant samples (finished samples plus additives) passed the copper corrosion test, as did most of the additive-free refinery samples. However, all fourteen of the additive-containing refinery samples failed. These fourteen samples were all finished sairples and contained AO-30. Since the six DFM samples which failed the test did not contain FSII, it is assumed that this additive did not play a part. Since the two pilot plant samples (containing AO-29) passed the test, and the fourteen refinery samples (containing AO-30) failed, questions are raised concerning the anti-oxidant additives which were used. These results need to be related to the sequence of operations in the refinery process and to the nature of the additives which were used. It seems probable that either there was a problem with the acid treatment process by which a corrosive species was produced which ended up in the finished samples, or that the additives used may have been contaminated. Both aspects may be involved. 

Free sulfur (17 ppm) and mercaptans (10 ppm) have been detected in the Shale-II JP-5. Model studies found that the combined presence of these two species, each at about the 10 ppm level, can cause failure of the copper corrosion test. The antioxidant, AO-30, exhibited indications of reinforcing the effects of the sulfur species in the model studies. 

An attempt was made to correct the copper corrosion problem by different types of fuel treatments (25). JP-5 samples were subjected to clay or silica gel filtration, or treatment with activated charcoal to remove the corrosive compounds. None of these treatments was successful. Samples were also treated with barium nitrate (to precipitate out sulfonates), sodium hydroxide (to extract mercaptans), and air bubbling to oxidize the corrosive compounds. These chemical treatments also were unsuccessful. However, JP-5 fuel (which failed the copper corrosion test) passed if benzotriazole, sometimes used to passivate copper surfaces, was added to the fuel in low concentrations (2 ppm) using FSII as a solvent. This technique is effective for reducing jet fuel attack on copper-nickel pipes used aboard aircraft carriers (26). 

Presence of small amounts of some sulfur compounds in certain refined products (gas and liquid) can have a corrosion effect on copper alloy components of users equipment that adversely affects their function. For example, copper corrosion products could cause plugging of metering and pilot valves. Consequently, product specifications may call for the product to pass a copper corrosion test such as ASTM D 1838, Test Method for Copper Strip Corrosion by Liquefied Petroleum (LP) Gases, or ASTM D 130, Test Method for Detection of Copper Corrosion from Petroleum Products by the Copper Strip Tarnish Test, or ASTM D 4048, Test Method for Detection of Copper Corrosion from Lubricating Grease. 

Road vehicles—Brake linings—Seizure to ferrous mating surface due to corrosion—Test procedure Soft soldering fluxes—Test methods—Part 12 Steel tube corrosion test Soft soldering fluxes—Test methods—Part 15 Copper corrosion test... 

Finally, other tests to control jet fuel corrosivity towards certain metals (copper and silver) are used in aviation. The corrosion test known as the copper strip (NF M 07-015) is conducted by immersion in a thermostatic bath at 100°C, under 7 bar pressure for two hours. The coloration should not exceed level 1 (light yellow) on a scale of reference. There is also the silver strip corrosion test (IP 227) required by British specifications (e.g., Rolls Royce) in conjunction with the use of special materials. The value obtained should be less than 1 after immersion at 50°C for four hours. 

If sulfur is a contaminant, its content can be measured, but it may suffice to characterize its effects by the copper strip corrosion test, or by the doctor test". 

Performance can be illustrated for example by the time necessary for deaeration or de-emulsification of oils, anti-rust properties, copper strip corrosion test, the flash point in closed or open cup, the cloud and pour points, the foaming characteristics, etc. 

Specifications for the principal LPG products are summarized in Table 4. Detailed specifications and test methods for LPG are pubHshed by the Gas Processor s Association (GPA) (3) and ASTM (4). The ASTM specification for special-duty propane and GPA specification for propane HD-5 apply to propane that is intended primarily for engine fuel. Because most domestic U.S. LPG is handled through copper tubing, which could fail if corroded, all products must pass the copper strip corrosion test. A test value of No. 1 represents a LPG noncorrosive to the copper. 

Vanadium is resistant to attack by hydrochloric or dilute sulfuric acid and to alkali solutions. It is also quite resistant to corrosion by seawater but is reactive toward nitric, hydrofluoric, or concentrated sulfuric acids. Galvanic corrosion tests mn in simulated seawater indicate that vanadium is anodic with respect to stainless steel and copper but cathodic to aluminum and magnesium. Vanadium exhibits corrosion resistance to Hquid metals, eg, bismuth and low oxygen sodium. 

Attack on metals can be a function of fuel components as well as of water and oxygen. Organic acids react with cadmium plating and 2inc coatings. Traces of H2S and free sulfur react with silver used in older piston pumps and with copper used in bearings and brass fittings. Specification limits by copper and silver strip corrosion tests are requited for fuels to forestall these reactions. 

The acid wash test consists of shaking a mixture of 96% sulfuric acid with benzene and comparing the color of the (lower) acid layer with a set of color standards. Other quaUtative tests include those for SO2 and H2S determination. The copper strip corrosion test indicates the presence of acidic or corrosive sulfur impurities. The test for thiophene is colorimetric. 

The CASS Test. In the copper-accelerated acetic acid salt spray (CASS) test (42), the positioning of the test surface is restricted to 15 2°, and the salt fog corrosivity is increased by increasing temperature and acidity, pH about 3.2, along with the addition of cupric chloride dihydrate. The CASS test is used extensively by the U.S. automobile industry for decorative nickel—chromium deposits, but is not common for other deposits or industries. Exposure cycle requirements are usually 22 hours, rarely more than 44 hours. Another corrosion test, now decreasing in use, for decorative nickel—chromium finishes is the Corrodkote test (43). This test utilizes a specific corrosive paste combined with a warm humidity cabinet test. Test cycles are usually 20 hours. 

The Electrolytic Corrosion Test. Also developed for use on nickel—chromium and copper—nickel—chromium decorative automobile parts is the electrolytic corrosion (EC) test (44). Plated specimens or parts are made anodic in a corrosive electrolyte under controlled conditions for 2 min, and then tested for penetration to the substrate. 

Amines remove the bulk of the H2S primary amines also remove the COj. Amine treating is not effective for removal of mercaptan. In addition, it cannot remove enough H2S to meet the copper strip corrosion test. For this reason, caustic treating is the final polishing step downstream of the amine units. Table 1-3 illustrates the chemistry of some of the important caustic reactions. 

Table 4.11 Atmospheric corrosion tests on copper and copper alloys...

Several extensive series of soil-corrosion tests have been carried out by the National Bureau of Standards in the United States, and the results have been summarised by Romanoflf. In one series two types of copper and ten copper alloys were exposed in fourteen different soils for periods up to 14 years. The results for the copper specimens are summarised in Table 4.12. 

Table 4.12 Soil-corrosion tests on copper by National Bureau of Standards and British Non-ferrous Metals Research Association...

As an undercoating for chromium, i.e. in place of nickel, copper is not to be recommended. On the other hand, both accelerated and outdoor corrosion tests have shown that a tin-bronze deposit, containing 80-90% copper, is considerably better for this purpose and it has been claimed to be approximately equal to nickel in this respect. 

Corrosion tests have shown that a system based on copper, double nickel and microcracked chromium gives good corrosion resistance, although automobile parts plated with microcracked chromium are not as easy to clean as those plated with crack-free chromium deposit. 

Various types of reference electrodes have been considered in Section 20.3, and the potentials of these electrodes and their variation with the activity of the electrolyte are listed in Table 21.7, Chapter 21. It is appropriate, however to point out here that the saturated calomel electrode (S.C.E.), the silver-silver chloride electrode and the copper-copper sulphate electrode are the most widely used in corrosion testing and monitoring. 

The significance of the corrosion potential in relation to the equilibrium potentials and kinetics of anodic and cathodic reactions has been considered in Section 1.4, but it is appropriate here to give some examples of its use in corrosion testing. Pourbaix has provided a survey of potential measurements in relation to the thermodynamics and kinetics of corrosion, and an example of how they can be used to assess the pitting propensity of copper in Brussels water is given in Section 1.6. 

Test method for porosity in gold platings on metal substrates by gas exposures Test method for half-cell potentials of uncoated reinforcing steel in concrete Method for detection of copper corrosion from petroleum products by the copper strip tarnish test... 

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