CZ32782U1 - Solution for producing pigment for repairing natural copper alloy patina - Google Patents

Description

Technical field

The invention relates to a color-modified brochantite-based pigment for repairing the natural patina of copper alloy objects.

BACKGROUND OF THE INVENTION

In an ordinary atmosphere, copper alloy objects are coated with a compact layer of corrosion products based on the brochantite CluSO4Oj. This protective and aesthetic layer is often damaged mechanically or chemically during restoration work. Otherwise, it may be necessary to replace whole parts, eg replacing damaged whole sheets from part of the roof covering. The possibility of replacing the missing patina is the powder pigment immobilized in the binder (paint, paint). Pigment to replace missing patches based on brochantite is commonly prepared by titrating a solution of “blue vitriol” CUSO4.5H2O with sodium hydroxide solution NaOH. This procedure has long been known (FitzGerald, K.P .; Nairn, J .; Atrens, A., The chemistry of copper patination. Corrosion Science 1998, 40 (12), 2029-2050). However, the obtained pure pigment has a shifted color to blue, and although it is chemically identical to the natural patina and equally chemically stable, it is not an aesthetically pleasing alternative.

The essence of the technical solution

This disadvantage is eliminated by the technical solution which consists in adding 1x10 ^-4 to 1x10 ^-3 mol.dm ^{-3 of} “green vitriol” I cSCU.VIPO to the basic solution of “blue vitriol” CUSO4.5H2O with a concentration of 1x10 ^-2 to 6x10 ^_1 mol. dm ' ³ . This solution is titrated with a solution of 1x10 ^-2 to 1 mol-dm ³ NaOH. The stock solution must be vigorously stirred when titrant is added. The titration rate shall not exceed 0,8 ml.min ¹ titrant per 100 ml of the stock solution. When the pH of the solution reaches 11, rapid filtration and washing of the solution is required. A delay of more than 3 minutes leads to the formation of CuO tenorite on the surface of the pigment particles and graying. If the filtration is done in a timely manner, the color of the pigment with trace addition of yellow ferric cation shifts the color of the resulting pigment from blue-green color to the pastel green color of natural patina.

Clarification of drawings

Giant. 1 Titration curve of copper sulphate stock solution with sodium hydroxide titrant. Marked pH suitable for beginning filtration of titrated solution.

Giant. 2 Color pigments in ClELab color space: “black dot” - natural patina; 'White point' - pigment produced by standard procedure; “Gray spot” - pigment produced by a modified process from a solution with the addition of ferrous sulphate.

Example of technical solution implementation

Example 1

A solution of 6x10 ¹ molardirr ³ CUSO4.5H2O and 1x10 ^-3 mol.dirr ³ FeSO4.7H2O was titrated with a 1 mol.din ³ NaOH solution at a titration rate of 0.8 ml.min ¹ . Upon reaching pH 11 the solution was immediately filtered and washed with distilled water on a Buchner vacuum funnel.

- 1 GB 32782 U1 (Fig. 1). The resulting pigment, after drying, has a color closer to natural patina than the standard solution without the addition of ferrous sulfate (Fig. 2).

Industrial applicability

The solution can be used for laboratory and industrial production of pigments for repairing restored objects from copper alloys.

Claims (1)

What is claimed is: 1. A solution for producing a copper pigment comprising 1 * 10 < ^-2 > 15 ^_1 moLdni 6xl0 ³ CuSO4.5H2O and lxlO ^-4 to ^-3 lxlO moLdni ³ FeSO4.7H2O.