Sodium chloride alternate immersion

Nickel-iron alloys are more resistant than iron to attack by solutions of various salts. In alternate immersion tests in 5% sodium chloride solution Fink and De Croly determined values of 2-8, 0-25 and 0-5 g m d for alloys containing 37, 80 and 100% nickel compared with 46 g m d for iron. Corrosion rates of about 0.4 g m d are reported by Hatfield for Fe-30Ni alloy exposed to solutions containing respectively 5 Vo magnesium sulphate, 10 Vo magnesium chloride and 10% sodium sulphate the same alloy corroded at a rate of about 1.2 g m d in 5% ammonium chloride. 

Material to be frozen can be fully immersed in a cold liquid. This might be a brine, in which case the material may have to be wrapped in a plastic bag to avoid contact with the liquid. The sodium chloride and glycol brines cannot be used cold enough to get complete freezing, so this may be a first pre-cooling stage before a final air blast. Alternatively, liquid nitrogen (- 196°C) or carbon dioxide (-78.5°C) can be sprayed onto the surface. 

Experimental CFTs were determined by Brigham and Tozer in three different ways based on chloride solutions two electrochemical and one chemical. In electrochemical testing in sodium chloride (NaCl) solution, the methods involved recording the current while either increasing the potential at suitable selected temperatures (apotentiodynamic test) or increasing the temperature at suitable fixed potentials (a potentiostatic test). Alternatively, a potential was established by the redox couple (Fe(in)/Fe(n) in a simple immersion test in ferric chloride solution. 

ASTM G44-88 (1988) Standard Practice for Evaluating Stress Corrosion Cracking Resistance of Metals and Alloys by Alternate Immersion in 3.5% Sodium Chloride Solution. 

FIG. 1—Corrosion rates of magnesium binary alloys determined in alternate immersion testing in 3 % sodium chloride [7]. 

Specific tests frequently used are (a) neutral 5 % Sodium Chloride salt spray (ASTM B 117, Test Method of Salt Spray (Fog) Testing), (b) 3.5 % Sodium Chloride by alternate immersion (ASTM G 44, Practice for Evaluating Stress Corrosion Cracking Resistance of Metals in 3.5 % Sodium Chloride Solution), and (c) exposure to various outdoor atmospheres. Guidelines for outdoor exposure are contained in ASTM G 50, Practice for Conducting Atmospheric Corrosion Tests on Metals. Generic types of atmospheres used are seacoast, industrial, urban, and rural. Sometimes specific geographical locations or local chemical conditions are important because they can produce unique results [2i],... 

Alternative atmospheric cabinet simulation tests are available, including ASTM G 87, Practice for Conducting Moist SO2 Tests and ASTM G 85, Practice for Modified Salt Spray Testing. Service in environments where humidity or moisture varies may be simulated by cyclic humidity or alternate immersion tests. See ASTM G 60, Test Method for Conducting Cyclic Humidity Tests and ASTM G 44, Practice for Exposure of Metals and Alloys by Alternate Immersion in Neutral 3.5 % Sodium Chloride Solution. 

Standard test method for performing a stress corrosion cracking test of low copper containing Al-Zn-Mg alloys in boiling 6% sodium chloride solution Standard practice for alternate immersion stress-corrosion testing in 3-5% sodium chloride solutions. 

Alternate immersion in 3.5% NaCl as described in ASTM G 44, Practice for Evaluating Stress-CotTOsion Cracking Resistance of Metals and Alloys in 3.5% Sodium Chloride Solution, This practice utilizes a 1 h cycle that includes a 10 min period of immersion in an aqueous solution of 3.5% NaCl or in substitute ocean water, followed by a 50 min emersion period. The 1 h cycle is continued 24 h/day for the duration required for the test material. Aluminum alloys are typically exposed from 10 to 90 days or longer. 

Alternate Immersion in 3.5% NoCl. Exposure to 3.5% sodium chloride or to substitute ocean water (ASTM D 1141) by alternate immosion (ASTM G 44) (see Table 1) is a widely used procedure for testing smooth specimens of aluminum alloys. Aeration of the specimens, achieved by the alternate immersion, enhances the corrosion potential (Ref 26) and produces more rapid SCC of most aluminum alloys than continuous immersion. The ASTM G 44 standard practice consists of a 1 h cycle that includes a 10 min soak in the aqueous solution followed by a SO min period out of solution in air at 27 °C (80 °F) and 45% relative humidity, during which time the specimens are air dried, lliis 1 h cycle is repeated continuously for the total number of days recommended for the particular alloy being tested. IVpically, aluminum alloys are exposed from 10 to 90 days, depending on the resistance of the alloy to corrosion by salt water. This test ntethod is widely used for testing most types of aluminum alloys with all types of smooth specimens. 

Alternate immersion exposure of metals and alloys in neutral 3.5% sodium chloride solution G44... 

To a mixture of 8.2 g of cyclohexene, 12.0 g of chloroform caution ), and 20 mL of 50% aqueous sodium hydroxide in a 125-mL Erlenmeyer flask containing a thermometer, add 0.2 g of benzyltriethylammonium chloride. Swirl the mixture to produce a thick emulsion. The temperature of the reaction will rise gradually at first and then markedly accelerate. As it approaches 60°C prepare to immerse the flask in an ice bath. With the flask alternately in and out of the ice bath, stir the thick paste and maintain the temperature between 50 and 60°C. After the exothermic reaction is com-... 

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