DE2101577A1 - Corrosion-protective primers - for iron and steel, contg anodic metals, graphite and/ r carbon black - Google Patents

Abstract

The primer consists of an organic and/or inorganic binder contg. anodic metal pigments (e.g. zinc) and solvents or diluents with pigment level pref. corresponding to the critical pigment volume conc. with addition of carbon pigments such as graphite and/or carbon black. Pref 20 - 50 vol. % of the metal pigment is replaced by the carbon pigment, which pref. consists of coarse graphite particles of over 40 microns dia. together with fine carbon black particles to fill the spaces left between the larger particles. Electrical conductivity of the film, which is of decisive importance in cathodic corrosion protection, is improved by power of ten.

Description

Hans J. Henning 85 Nuremberg 33, January 12, 1971

Motterstrasse 124

Erosion scratch primer

The invention relates to a corrosion protection primer for cathodic corrosion protection of iron and steel parts. Such primers must have anodic metal pigments Contained in sufficient quantities to provide effective protection. The anti-corrosion effect of the anode metals is based on their ignoble character compared to iron in connection with electrolytic processes. With an electrically conductive connection of the iron or steel part to be protected with e.g. zinc dust, Zn in the galvanic element Fe / Zn acts as an anode and gives thus its electrons are transferred to the iron. These electrons prevent or possibly reduce the formation of Fe ions already existing Fe ions back to metallic iron. The transport of the electrons is determined by the conductivity of the electrically conductive pigments present in the paint film. Heine's zinc is a real metallic conductor, wäh = Meanwhile, fine zinc dust is covered with an at least monomolecular zinc oxide and / or carbonate layer, which acts as a conductor ability strongly depresses. If the pigment particles are coated with a binder, the conductivity is further reduced diminishes.

The aim of this invention is to improve the electrical conductivity of the cured or dried paint film with the closest packing of pigments and a degree of pigmentation that corresponds to the KPVK. KPVK means critical pigment volume concentration; this denotes the degree of pigmentation at which neither an excess of binder nor of pigment is present hand is.

209831/0862

There are numerous patents, e.g. a) and b), and publications, e.g. c), known in the field of cathodic corrosion protection, from which it can be clearly seen that the electrical conductivity of the paint film is of decisive importance for radio operation tion of the cathodic corrosion protection is a significant improvement of the currently known primers in this regard were de has not yet been published.

The improvement in electrical conductivity for the same layer = According to the invention, a thickness of at least a power of ten is used once achieved by the fact that part of the zinc dust pigment is replaced by Koh = lenstoff — pigment such as graphite and / or carbon black with at least 98'ί C-Ge = stop and largest primary grain diameter (the larger the diameter, the better the electrical conductivity of the carbon black concerned) is replaced.

Another way to measure the electrical conductivity of the paint = to increase film is achieved according to the invention in that in the "Cavities" between the pigments with a relatively large primary grain diameter (e.g. greater than 1 / u) known green = dations are filled with binder, additionally carbon black pigment with a very small primary particle diameter (e.g. smaller than 30 myu) is installed. This measure results in opposite the pigment combination mentioned first has both a further Er = increase of the electrical conductivity as well as a greater pigment = packing density and thereby a further improvement of the cathodic corrosion protection.

a) AS 1 240 205; Registration: 03/15/1963
Paints for corrosion protection

b) OS 1,519,212; Registration: February 6, 1965
Anti-rust agents

c) K. Sautner, cathodic protection of buried systems, messages from the Forschungsges. Sheet metal processing e.V. Edition I5 / 16 I960

209831/0862

Claims (3)

Claims 1. A corrosion protection primer of the following composition:
Organic and / or inorganic binders;
Anode metal pigments (all metals are considered to be anode metals
which are above Fe in the electrochemical series, such as Mg, Al, Mn, Zn, Cr), their mixtures and / or alloys in pigment form, hereinafter referred to collectively as anodic metal pigments; Paint auxiliaries and solvents or thinners; their degree of pigmentation in relation to the anodic ones Metal pigments preferably of the KPVE (critical pigment volume = men concentration), characterized, that this primer additionally carbon-pig = such as graphite and / or carbon black pigments. 2. A primer according to claim 1, characterized in that
a part, preferably 20-50 vol- $, of the anodic metal pigments by means of graphite and / or carbon black pigments
is replaced. 3. A primer according to claim i, characterized in that
a part, preferably 10-40% by volume, of the anodic metal pigments due to electrically non-conductive and / or poorly conductive pigments and / or fillers, such as zinc oxide, magnesium oxide, chromium-3-oxide, Liagnesium silicate, calcium silicate, etc.,
is replaced. 209831/0862 4 "A primer according to claim 1, characterized in that this primer has the following pigment combination: Anodic metal pigments with a primary grain diameter of less than 40 / u, preferably less than 3 / u a degree of pigmentation below the CPVK; Graphite with a primary grain diameter greater than 40 / u, preferably 40-80 / u, with a degree of pigmentation before = should preferably correspond to the KPVIC; and carbon black pigments, 209831/0862