CS241719B1 - A method for detecting a corrosion site on a steel surface - Google Patents

Abstract

The purpose is to enable the precise localization of corrosion directly on the steel part, without the need to use indicator paper for this purpose. The stated purpose is achieved by applying a test solution mixed with a sufficiently transparent adhesive to the tested steel surface, which would fix the test solution in the applied place, and thus allow the visual detection of the corrosion site, either by a pronounced coloration or by a changed color of the fixed test solution. The solution can be used in all areas where it is necessary to detect surface corrosion that is irregularly or pittedly distributed on the examined surface.

Description

The invention relates to a method for detecting a corrosion site, in particular point and other irregular corrosion, on a steel surface by changing the color of a test solution by changing the depasivation potential at the corrosion site.

Methods for testing the resistance of stainless steels to irregular corrosion, in particular point corrosion, on the steel surface are based on the effect of test solutions containing halide, most often chloride, at a sufficiently positive potential. The test solution component must have a suitable redox potential in the aqueous solution. So far, a filter paper was added to the test solution, which was applied to the test site of the steel surface, and after a period of time, e.g. This method had the disadvantage that the test paper had to be precisely positioned at the designated point on the surface of the steel component, which is sometimes quite difficult. The use of the method has been problematic in the rugged steel surface, in cracks, bends, in sleeves, sockets, joints such as tubesheet tubes, etc., where irregular corrosion often occurs.

These drawbacks are largely eliminated by the method of the invention, which consists in applying a test solution in a mixture with a sufficiently transparent adhesive to the test surface of the steel.

This method is particularly advantageous when detecting irregular corrosion on a rugged steel surface, in cracks, bends in sleeves, extensions on pipe-tube joints and other joints. The method according to the invention makes it possible to precisely locate the corrosion directly on the steel part, without the need to use indicator paper for this purpose, and thus difficult to reproduce the location of the corrosion. The method according to the invention allows further enhancement of coloring when the test solution is used in a mixture not only with the adhesive but also with the powdered sorbent.

An example of the method of the invention is the application of one part by weight of an aqueous test solution with one part of gelatin to a rugged machine part made of marsitic stainless steel Cr 11 Ni 3. NaCl, 40 wt. KNO3, 2 wt. % acetic acid, 5 wt. Ks [Fe (CNJe) and 5% by weight K4Fe (CN) 6/3 H 3 O. The blue color of Turnbull blue appears at the corroded sites 15 minutes after application, another example is to apply three parts by weight of the aqueous test solution below. with one part of glue and one part of silica gel for the rugged austenitic steel part of Cr 18 Ni 12 Mo 2 Ti Test solution contains: 40% by weight of NaCl, 2% by weight of acetic acid, 9% by weight of Ks [Fe (CN) 6] and 1 wt% K4 [Fe (CN) e] .3 H2O The indication is the same as in the first case to remove the chloride ion from the metal surface, neutralize the remainder of the liquid on the metal surface with ammonia solution and at least three times. rinse with distilled water.

The invention can be used in mechanical engineering and wherever it is necessary to detect surface corrosion irregularly or pits distributed on the test surface.

Claims (4)

SUBJECT A method for determining the corrosion site on a steel surface by changing the color of a test solution, characterized in that a test solution in a mixture with a sufficiently transparent adhesive is applied to the test surface of the steel. 2. The method of claim 1, wherein the adhesive is either gelatin or glue, or collodion, or starch grease, or water glass, or egg white, or agar. YNÁLEZU 3. A method according to claim 1, characterized in that a test solution in a mixture of sufficiently transparent adhesive and powdered sorbent is applied to the steel surface to be tested. 4. The process of claim 3 wherein the sorbent is either silica gel or alumina, or diatomaceous earth, or molecular sieve, or gypsum, or chalk.