CS223451B1 - A method for determining the thickness of a tin, a coating and an intermediate layer formed on iron and copper substrates - Google Patents

Abstract

The invention relates to a method for determining the thickness of a tin coating and an intermediate layer on iron and copper substrates. The essence of the assay method is that the sample dissolves anodically at a constant temperature and constant anotic current density in a sulfuric acid solution. From the time variations of the potential, the thickness of the tin layer and the interlayer is calculated so that with an active anode area of 1 cm, 1 As dissolves a layer of tin of constant thickness, respectively. other constant thicknesses of intermetallic copper and tin compounds and intermetallic iron and tin compounds. The invention has applications in the food and electrical industries.

Description

The invention solves the epdeob of the determination of the tin coating thickness and the interlayer, formed by heat or electrolytically on iron reep · steel and copper substrates ·

When forming tin coatings on an iron and modified basis, it is necessary to know the thickness of the deposited tin layer and the intercoat in terms of both the anticorrosion properties of the coating as well as economically. At present the tin layer thickness is determined microscopically and electrolytically microanalysers. The disadvantage of microscopic determination of the tin train thickness is the sagging and difficulty of preparing a quality cross-section of the sample cross section. · Thin coating deforms during grinding, which significantly distorts the results · Using a coulometric method only tin coating thickness can be determined the sample does not contain an intermediate layer. The X-ray microanalyzer can be determined with sufficient accuracy only if it is greater than 5 days. · In practice tinplate and tinplate used in engineering have a substantially lower interlayer thickness.

The above-mentioned disadvantages are substantially eliminated by the method of etching the tin coating thickness and the intermediate gate formed on the iron and copper supports according to the invention, which consists in that the sample dissolves anodically at room temperature and constant anodic current density of 15 to 40 mA / cm solution of 10% sulfuric acid and from time changes of potential e and calculates the thickness of tin layer and intermediate

On the measured potential-time curve, two waves are clearly visible · The first wave corresponds to the tin layer dissolution · Then the working electrode / sample / potential changes rapidly to the value at which the next anodic event begins, i.e. After this process, the pad will start to melt ·

From the measured £ - t curve, the known dimensions of the anode surface (sample area that is immersed in the electrolyte) and the known value of the current used, the tin coating and interlayer thickness is calculated by Faraday's law.

223,451 layers, taking into account the results obtained by the authors of the diffusion study in the iron-tin and mecetin systems.

With an 'active flat anode of 1 cm', it dissolves a 1 As layer of 0.84 tin. and 0.51 µm of an intermeeal copper-tin compound of 39% loading. medium and 61% by weight of tin and an intermstalic copper and tin compound having a 61.6% by weight composition. copper and 38.4 wt% > tin, respectively, · 0.68 µm of an iron-tin compound of 19% by weight iron and 81% by weight <> t · t ·

This method of galvanosthetic anodic dissolution of tin coatings on iron and copper bases is a simple, easy and epolytic determination of tin thickness. layer and cross-industry, whose knowledge is necessary both in assessing the quality of the protective properties of the coating and in terms of

Example 1

Sample of tinned steel. wire is immersed in 10% sulfuric acid solution · Submerged sample area is 0.276 cm -1 · Together with the sample the carbon electrode is immersed in the solution, ^{p p h h} is 4 cm ² · ^S cumulated sample is connected to the positive pole of the source direct current and carbon electrode to the negative pole. An electrical current of 5'nA is allowed to flow between the electrodes, which corresponds to an anodic current density (i.e., current density per test sample) of 18.1 mA cm @ ² · The voltage difference between the electrodes is recorded on the recorder. * ekokovsj changes in electrical potential ea measured 78.38 s, This corresponds to a tin layer thickness of 1.2 <m · Second wave recorded at. It took 36.98% to the extent that the layer of inthermic compounds contains 19% by weight. % of iron and 81 wt.% tin, the measured second wave corresponds to the thickness of the intermeeal layer. 0.46 ^ um ·

Example 2

Determination of the tin layer thickness and the intermediate layer on the copper base is determined experimentally in a similar manner to that described in Example 1.

223 451

Anodic solvent-melting "of the tin coating on the basis of the m mede.no therein an active surface area of 0.251 cm ^fc 10% sulfuric acid, the ^{anodically j} ^ People's density of ¹ * 9 ^ 92 mA cm ² and a case rozpúSUani" tin layer t _x = 66, 88 is an intermediate consisting of intermatal compounds of medium and tin having a composition of 61% by weight, medium and 38.4% by weight. tin and an intermediate compound of the medium and tin containing 39% by weight of the medium and 61% by weight. tin, t's 88 * 48 s, the thickness of the tin layer was 2.8 µm and the resistance was 0.90 μυη.

Claims (1)

Method for determining the thickness of the tin layer and the interlayer on iron and copper substrates, characterized in that it is characterized by &lt; 1 &gt; the sample dissolves anodically at. . teplete ^ * ^'to tne ° affinities ^{n j n} ° dlckej Průšová geese theta ¹ 5-40 mA cm ^ ² in a solution of 10 J broad, ester, and the temporal changes of the potential of the ^ Pomt thickness. tin. layers and layers »