Salt mist

Test Kb. Salt mist, cyclic (sodium chloride solution)... 

There is a standard, ISO 4611 [19], specifically for examining exposure to damp heat, water spray and salt mist, which specifies three types of exposure corresponding to those three conditions. The standard gives general guidance only and refers to various IEC and ISO publications for greater detail. 

A water spray test is similar to damp heat except that there is the constant presence of small water droplets. The test is made using essentially similar equipment to that for the salt mist test. 

Special cabinets are used for salt mist exposure in which a fine mist of a sodium chloride solution is produced at specified conditions. Change in mass or any physical property can be measured. This type of exposure has its origins in the determination of corrosion resistance rather than changes in bulk properties. 

ISO 4611, Plastics - Determination of the effects of exposure to damp heat, water spray and salt mist, 1987. 

Accelerated testing of the protective ability of the preservation of hardware by inhibited plastics is carried out by standard methods at the branch, state or international level. The real conditions of storage and transportation of preserved articles are simulated during these tests. With this aim, the system is subjected to a cyclic loading with a salt mist in dry or wet conditions with [87-89] and without moisture condensation [86]. Aside from this, certain simplified non-standardized procedures take into account the type and purpose of preserved hardware as well as the required conditions, aims and terms of preservation [49-51,90-92]. 

The standardized tests use special apparatuses called exposure cabinets for exposure to salt mist, heat and moisture. Normative documents contain special sections specif 4ng the form, size and quantity of metal samples along with their preparation procedure for the tests. Preparation of the samples... 

Russian Standard 9.509-88 [12] presupposes tougher test conditions that include the effect of salt mist, elevated temperature and humidity with and without moisture condensation, the effect of cold and endurance under normal conditions (Table 1.10). A single testing cycle corresponds to the real storage conditions or transportation of the samples indoors with corresponding ventilation without regulation similar to the regions with moderate and cold climate for six months. 

Test Methods Salt Mist Elevated Temperature Without Moisture Condensation With Moisture Condensation Cold Conditions... 

ISO 14993 2001. Corrosion of Metals and Alloys - Accelerated Testing Involving Cyclic Exposure to Salt Mist, Dry and Wet Conditions. Geneva, ISO Copyright Office, 2001. 

ISO TC 156 WG7/N137, Accelerated corrosion testing involving cyclic exposure to salt mist, dry and wet conditions. Draft International Standard, International Organization for Standardization, 1998. 

Monday Through Friday Salt mist appiixriions In ambient envboninenl (25C 1- 3C, 40-50% RH) every 1.5 hours (4 appicaions total for a total time of 4.5 hours) SaH consisis Ob 0.9 %Nad 0.1 %CaCI, 0.2S%NaHCO, pH. 6-8... 

Fertilizer, animal and human activity, detergents Sea salt mist, road salt areas... 

Protection against corrosion of iron and steel in structures—Zinc and aluminium coatings—Guidelines Corrosion of metals and alloys— Accelerated testing involving cyclic exposure to salt mist, dry" and "wet conditions... 

The most damaging natural atmosphere for aluminum is that of a seacoast, with the severest corrosion taking place within 0.5 mile (0.8 km) of the shore line. Corrosive effects will be greatly reduced at distances of 2-5 miles (3-8 km) from the shore. Prevailing wind directions and the roughness of the surf determine the extent of the corrosive effect, which controls how far inland actual salt mist will be carried. In order to maintain the shining metallic surface of aluminum in a seacoast atmosphere, pure aluminum as well as some aluminum alloys must be protected with a coat of clear lacquer or an anodized coating. 

Table 2 Salt mist corrosion performance of various steels and coatings...

Exfoliation of susceptible alloys occurs in many outdoor environments, but it develops most rapidly in marine exposure (Fig. 8). The voluminous corrosion products that promote the delamination of the metal form most readily under conditions of intermittent spraying with salt mist or intermittent iimnersion in salt water. The exfoliation effects are stimulated further by acidic deposits (as from gases exhausted by gasoline-burning aircraft engines) and by elevated temperatures. 

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