Hydrochloric acid spray test

It was reported that the early salt spray tests (ASTM B 117) did not yield useful results when applied to chromium-plated brass specimens, while the results of a hydrochloric acid spray test were claimed to be in good agreement with the behavior of this material during weathering [10. ... 

The test solution should not contain more than 5 per cent (v/v) concentrated hydrochloric acid and must have a pH < 2. It is spotted on a paper strip and allowed to evaporate for 10-15 minutes. Diffusion of the solvent takes place in an atmosphere saturated with respect to the vapour of a saturated solution of methyl acetate in water, and the temperature is maintained constant at 22°. The solvent moves sufficiently far in 20-30 minutes to effect a complete separation. After evaporation of the solvent, the strip is made alkaline by exposure to ammonia vapour and then sprayed with a 1 per cent solution of diphenyl-carbazide in alcohol. Mercury is indicated by a narrow blue band in the dry solvent front. 

If 1,1,1-trichloroethane is not properly stabilized it forms hydrochloric acid in the presence of aluminum. HCl corrodes aluminum. The presence of free water invalidates the result of this test. An aluminum coupon is scratched beneafli flie surface of a solvent The coupon is observed for 10 min and 1 h and flie degree of corrosion is recorded in form of pass (no reaction) or fail (gas bubbles, color formation, or metal corrosion). The test is important to cleaning operations because aluminum should not be used for parts of machines (pumps, tanks, valves, spray equipment) in contact with corrosive solvent. 

The current salt spray test, in which the plated specimen is exposed to a spray or fog of sodium chloride solution, is the most widely used accelerated corrosion test for coatings, and various procedures have acceptance tests in standard specifications in numerous countries. Over the years, the procedure has employed sodium chloride solutions of concentrations between 3 and 20 %, sometimes with the addition of hydrochloric acid or hydrogen peroxide. The salt spray test [ASTM B 117, Test Method of Salt Spray (Fog) Testing] has largely fallen into disrepute because of the recognition that its reproducibility and correlation with outdoor exj>osure were often poor. Cyclic salt spray testing as well as alternate electrolytes such as the "prohesion test solution have been found to produce more realistic results. 

A solution of 1.7 to 2.0 % hydrochloric acid is sprayed for 5 h at room temperature with the test specimens left in the test chamber for an additional 10 h without spraying. 

Procedure. One drop of the test solution is spotted on filter paper and dried. The paper is then dipped into or sprayed with a 1 % solution of methyl violet. After about 30 seconds, the paper is sprayed with a solution at 12 g of ammonium molybdate in 150 ml of water acidified with 35 ml of 10 N hydrochloric acid. Phosphates give a blue spot. 

Procedure The tested substance (0.2 g) and 2.5 g of KOH are heated in a glass tube at 360 — 370 °C for 3-5 min. After cooling, 5 ml of water are added, and the mixture is stirred with a glass rod and extracted with an equal part of benzene. The aqueous phase is acidified with hydrochloric acid (test with Congo red) and extracted with 5 ml of hexane. The hexane solution is applied directly on the chromatogram, which is then run in the formamide/hexane or formamide/hexane-benzene (3 2) system (p. 198). Detection is carried out by spraying with a diazonium salt. 

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