Coated substrates

A body having a substrate surface which comprises corrodible material and on which substrate surface is present a coherent protective layer of an anti-corrosion composition which comprises a solid matrix of electrical conductivity .gtoreq.10.sup.-6 mho cm.sup.-1 and formed by reaction between at least water-soluble Bronsted acid and at least one Lewis base in which matrix is incorporated an elemental metal, or an alloy thereof, the matrix and metal being effective in service as electrolyte and sacrificial anode, respectively.

This invention relates to coated substrates; more particularly, this 
invention relates to substrates which are coated and thereby protected 
from corrosive fluid media; to coating compositions therefor; and to 
processes for coating substrates with such coating compositions. 
There are considerable problems in economically protecting bodies, 
particularly structural bodies, in contact with aqueous media from 
corrosion. This is particularly the case wherein the bodies comprise steel 
and the contacting medium is sea water. Such marine structural bodies 
(which include sea-based oil rigs; wet and dry docks; piers and ships) can 
be afforded some cathodic protection below the sea line either by applying 
thereto a positive electric potential or by, in effect, incorporating them 
in a galvanic cell which also comprises sacrificial anodes, typically of 
aluminum, magnesium or zinc, and sea water, as electrolyte. However, above 
the sea line, especially in the so-called "splash zone" where not only 
does the water level rise and fall but also the corrosion process seems at 
its most vigorous, this expedient is not available and it is necessary to 
resort to coating this region of the structural body, an expensive 
procedure. Moreover, such structural bodies are liable to mechanical 
damage, for example by accidental collision; in consequence of this, the 
integrity of such coatings is put at risk. Furthermore, the surfaces of 
structural bodies in the splash zone are necessarily intermittently wet 
and cannot be coated with currently available, hydrophobic protective 
paints. 
This invention seeks to provide a coating which will overcome or minimise 
the aforesaid problems. 
Accordingly, the present invention provides a body having a corrosion-prone 
substrate and on which substrate surface is present a coherent protective 
layer of an anti-corrosion composition which comprises a solid matrix of 
electrical conductivity .gtoreq.10.sup.-6 mho cm.sup.-1 and formed by 
reaction between at least one water-soluble Bronsted acid, preferably a 
homo- or copolymer of an unsaturated Bronsted acid, and at least one Lewis 
base in which matrix is incorporated, preferably particulate, elemental 
metal, or an alloy thereof, the matrix and metal being effective in 
service as electrolyte and sacrificial anode, respectively. That is to 
say, this invention provides a method of coating a body comprising 
corrodible material with a solid electrolyte galvanic half-cell; and to a 
body so coated. 
While the body having the substrate surface may have small dimensions, the 
present invention is of particular advantage in its application to bodies 
of large dimension, especially structural bodies as aforementioned. The 
term "body" as used herein may include bars, strips, sheets, rods, tubes 
and other cross-sections of solid or hollow stock as well as structures 
fabricated therefrom. The term "tube" as used herein may include any 
closed or open-ended elongate hollow stock of substantially constant 
cross-section, desirably with an axis of symmetry; for example elongate 
hollow stock of substantially constant circular, elliptical, square, 
rectangular or triangular cross-section. 
The body may have one or more surfaces, which may be internally located 
surfaces, which comprise corrodible material. The or each such surface 
should have a coherent protective layer in accordance with the invention 
at least in the or each region which is in, or may come into, contact with 
a corrosive medium; for example, sea water. Desirably, all such surfaces 
should have a coherent protective layer as aforesaid over substantially 
their entire extent. 
The corrodible material is usually electropositive metal and generally 
comprises substantially the entire surface. The invention is of 
particular, but not exclusive, relevance to a ferrous metal substrate 
surface; for example, a steel such as a structural steel. 
The solid matrix is preferably hydrophilic in order to act in service (for 
example, in exposure to sea water) as an electrolyte. Good results are 
found to be obtained when the solid matrix comprises or, preferably, 
consists of, a cement. 
The term "cement" as used herein means the coherent mass formed by reaction 
at a temperature below 250.degree. C., preferably below 100.degree. C., 
especially at ambient temperature, from at least one settable substance 
(but excludes covalently cross-linked organic thermoset materials) rather 
than the cement-forming component(s) themselves. It is desirable that the 
settable substance is capable of adhesively binding the, preferably 
particulate, elemental metal, or alloy thereof. 
The cement is one in which at least one cement-forming component is a 
water-soluble Bronsted acid, preferably a homo- or copolymer of an 
unsaturated Bronsted acid, and at least one other cement-forming component 
is a Lewis base, preferably a Bronsted base. 
By "Bronsted acid" is meant herein a substance which is a proton donor; by 
"Bronsted base" is meant herein a substance which is a proton acceptor. By 
"Lewis base" is meant herein an electron donor and includes a Bronsted 
base. 
Such water-soluble Bronsted acids include a mineral acid, an acid salt, a 
polyfunctional carboxylic acid, a polyfunctional phenol, a homo- or 
copolymer of an unsaturated carboxylic acid, a homo- or copolymer of an 
unsaturated sulphonic acid, or a hydrolysable precursor thereof. The term 
"hydrolysable precursor" as used herein includes any species, such as an 
anhydride, an acid chloride or an acid amide, which is transformed on 
hydrolysis to the required acid cement-forming component. Suitable 
examples of mineral acids include phosphoric acids such as orthophosphoric 
acid, pyro-phosphoric acid and meta-phosphoric acids, sulphuric acid, 
nitric acid and hydrohalic acids, such as hydrochloric acid, with 
phosphoric acids being preferred. Examples of acid salts include the 
hydrogen and dihydrogen phosphates, bisulphates, and bifluorides, 
especially the alkali metal hydrogen and dihydrogen phosphates. Examples 
of polyfunctional organic carboxylic acids and polyfunctional phenols 
include the following polybasic acids: malonic, mesoxalic, succinic, 
glutaric, adipic, pimelic, suberic, azeaic, sebacic, malic, citric, 
tartaric, tartronic, tricarbballylic, maleic, fumaric, citraconic, 
mesaconic, itaconic, glutaconic, muconic, aconitic, ortho-, iso- and 
tere-phthalic, gallic, tannic and mellitic acids, catechol, resorcinol, 
quinol, pyrogallol, hydroxyquinol and phloroglucinol. Other polyfunctional 
organic carboxylic acids and phenols which are not polybasic but are 
suitable as acid cement-forming components include hydroxycarboxylic acids 
and ketoacids. Examples are lactic, pyruvic, 2-hydroxyisobutyric, 
2-hydroxycyclohexane carboxylic, 2-hydroxy-2-phenyl propionic, 
diphenylhydroxyacetic, 2-hydroxybenzoic, 3-hydroxybenzoic and 
4-hydroxybenzoic acids, eugenol and salicylaldehyde. Examples of homo- or 
copolymers of an unsaturated carboxylic acid include those prepared by the 
homopolymerisation or copolymerisation of aconitic acid, acrylic acid, 
citraconic acid, fumaric acid, glutaconic acid, itaconic acid, maleic 
acid, mesaconic acid, methacrylic acid, muconic acid and tiglic acid, and 
the copolymerisation of these acids with other unsaturated aliphatic 
monomers for example vinyl monomers, such as vinyl hydrocarbon monomers, 
vinyl ethers, acrylamide or acrylonitrile. Particularly noteworthy are the 
homopolymers of acrylic acid and its copolymers particularly copolymers of 
acrylic acid and itaconic acid, especially those described and claimed in 
U.K. Pat. No. 1484454. Good results have also been obtained using a 
copolymer of vinyl methyl ether and maleic acid. Examples of homo- or 
copolymers of an unsaturated sulphonic acid include those prepared by the 
homopolymerisation or copolymerisation of ethylene sulphonic acid. 
It is also possible to use a hydrolysable precursor of such polymers, for 
example a poly(carboxylic acid anhydride); furthermore, polyacrylic acids 
may be prepared by hydrolysis of corresponding polyacrylonitrile or 
anhydride. The hydrolysable precursor of a poly(carboxylic acid) may be a 
homopolymer of an unsaturated carboxylic acid or a copolymer with an 
above-mentioned other carboxylic acid or anhydride thereof, or a copolymer 
of an unsaturated carboxylic acid anhydride with an unsaturated aliphatic 
monomer, for example vinyl monomers, such as vinyl hydrocarbon monomers, 
linear or cyclic vinyl ethers, acrylamide or acrylonitrile, for example 
pyran copolymer. Good results may be obtained by using homopolymers of 
maleic anhydride or vinyl orthophthalic anhydride, or copolymers thereof, 
especially, block copolymers thereof, with ethylene, propylene, butenes, 
styrene and vinyl methyl ether. Mixtures of such components may be used. 
Preferably, the acid cement-forming component is in aqueous solution. 
It is to be understood, however, that both from the standpoints of 
availability and of good results, polyacrylic acid is the preferred 
Bronsted acid used in the formation of the solid matrix of this invention. 
The cement is also formed from a base cement-forming component. At least a 
portion of Bronsted base may be replaced by a filler, suitably an inert 
filler as disclosed in GB No. 1504520; for example, a refractory such as a 
transition metal oxide, for example an iron oxide, or brick dust. Where 
all of the Bronsted base is replaced by a filler another Lewis base must 
be present. Suitable Lewis bases may include an elemental metal, or an 
alloy thereof; for example a portion of that elemental metal, such as 
zinc, or an alloy thereof, which in service acts as sacrificial anode. 
Such systems are of particular utility where an enhanced working time is 
required; for example, in brush coating loci of substantial area. 
The cement is preferably formed from a base cement-forming component which 
comprises a basic or amphoteric oxide or hydroxide, or a salt of weak or 
volatile acid. There are many basic or amphoteric oxides or hydroxides 
which can form cements with at least one of the acid cement-forming 
components defined above; examples include Li.sub.2 O (other Group IA 
oxides or hydroxides tend to give materials whicha re too soluble in 
aqueous media), Group IIA oxides, preferably calcined, such as MgO, 
"Ti(OH).sub.4 ", "Zr(OH).sub.4 ", V.sub.2 O.sub.5, Cu.sub.2 O, CuO, ZnO, 
preferably calcined, Al.sub.2 O.sub.3.times.H.sub.2 O and SnO.sub.2. Salts 
of weak or volatile acids include carbonates, monocarboxylates, such as 
acetates and halides such as the halides of Mg, Ca, Ba, Th, Ti, Zr, Al and 
Sn. They also include extensive class of monomeric and polymeric 
(alumino)silicates, (alumino)phosphates and (alumino)borates which include 
the acid reactive natural and synthetic minerals and ion-leachable 
glasses. By "(alumino)silicate" is meant herein a silicate or an 
aluminosilicate; by "(alumino)-phosphate" is meant herein a phosphate or 
an aluminophosphate; by "(alumino)borate" is meant herein a borate or an 
aluminoborate. Examples of ion-leachable glasses include those glasses 
wherein the principal acidic oxide is silica (although the glass may also 
contain minor amounts of other anhydrides such as phosphorus pentoxide and 
boric oxide), and wherein the principal basic oxide in the glass is 
alumina which, although it has amphoteric properties, can be considered 
for the purposes of the present invention solely as a basic oxide. Such 
glasses include those from the systems SiO.sub.2 --Al.sub.2 O.sub.3 --CaO, 
SiO.sub.2 --Al.sub.2 O.sub.3 --CaF.sub.2, SiO.sub.2 --Al.sub.2 O.sub.3 
--CaO--CaF.sub.2, SiO.sub.2 --Al.sub.2 O.sub.3 --CaF.sub.2 --P.sub.2 
O.sub.5 and SiO.sub.2 --Al.sub.2 O.sub.3 --CaO--P.sub.2 O.sub.5. 
Particularly preferred glasses fall within the composition range of 10 to 
65% w/w silica and 15 to 50% w/w alumina. The glass desirably contains at 
least one other basic oxide, preferably calcium oxide, which may be 
present in the glass composition in an amount from 0 to 55% w/w. The 
calcium oxide may be partly or wholly replaced by sodium oxide or other 
basic oxide or a mixture of basic oxides. The presence of sodium oxide can 
be desirable in increasing the solubility of the resulting cement. 
Preferred glasses for use in the present invention containing alumina, 
silica and calcium oxide are the gehlenite and anorthite glasses, and in 
general glasses falling within the composition range 10 to 65% w/w silica, 
15 to 50% w/w alumina and 0 to 50% w/w calcium oxide. 
Other galsses suitable for use in the present invention may contain 
fluoride, suitably up to 15% by weight, preferably less than 10% by 
weight. A class of fluoroaluminosilicate glasses particularly suited to 
this invention are those wherein the ratio by weight of silica to alumina 
is from 1.5 to 2.0 and the ratio by weight of fluorine to alumina is from 
0.6 to 2.5 or wherein the ratio by weight of silica to alumina is from 0.5 
to 1.5 and the ratio by weight of fluorine to alumina is from 0.25 to 2.0. 
Other glasses include those disclosed in DE-OS No. 2750326 in J. Oral 
Rehabilitation, 10, pp 393-398 (1973); and in Ind. Eng. Chem. Prod. Res. 
Dev, 19 pp 263-270 (1980). 
It is to be understood, however, that both from the standpoints of 
availability and of good results, zinc oxide is the preferred Bronsted 
base used in the formation of the solid matrix of this invention. 
Mixtures of such components may be used. 
It is noted that, apart from cement-forming components of unequivocal 
acidity or basicity, certain components may react as acid cement-forming 
components under a given set of reaction conditions while reacting as base 
cement-forming components under a different set of reaction conditions. 
The elemental metal, or alloy thereof, should not only be more 
electropositive than the corrodible material but should also, in service, 
be able to function as a sacrificial anode. Where the corrodible material 
comprises ferrous metal the elemental metal, or alloy thereof, may be any 
metal with a standard electrode potential (E.sub.o) at 25.degree. C. less 
(greater negative value) than -0.44 volt. Examples include Mg, Ca, Al, Mn, 
Zn and alloys thereof including Mg/Al and Al bronzes, with Zn being the 
metal of choice in practice: Al appears to be passive while the other 
metals, in forms readily available, are too active. The elemental metal, 
or alloy thereof, may be particulate, including flake, fibrous or sheet in 
form. The average particle size of the elemental metal, or alloy thereof, 
is desirably in the range from 0.1.mu. to 100.mu., preferably from 1.mu. 
to 50.mu.. Where their average particle size is below 0.1.mu. there are 
problems of availability; moreover, the particles tend to aggregate which 
has a deleterious effect on mixing. Where their average particle size is 
above 100 .mu. the integrity of the protective layer is impaired. An 
average particle size of from 5.mu. to 20.mu. is generally very suitable. 
For optimum effectiveness, it is generally desirable to incorporate as 
much of the elemental metal, or alloy thereof, into the solid matrix as is 
possible. It is preferred to incorporate at least 10% by weight of the 
weight of the protective layer and as much as 90% by weight can be 
incorporated with advantage. 
It is also possible to form the elemental metal, or alloy thereof, and the 
glass cement-forming component as a cermet; for example, by mixing the two 
components; compressing the mixture and heating the compressed mixture in 
a vacuum furnace to prevent oxidation; and regrinding the frit so formed 
to the requisite particle size. 
It is often desirable to incorporate into the matrix-forming mix an oxidant 
which appears to act as a depolarising agent; for example, manganese 
dioxide, permanganate, chromate, dichromate or bismuthate ion. This may 
have the effect of preventing gross evolution of hydrogen gas which can 
cause bubbles to form under the protective layer thereby causing its 
spalling. Typically, no more than 5% by weight of the elemental metal, or 
alloy thereof, of the oxidant need be present. 
It is also often desirable, in order to enhance working time, especially in 
brush coating, to incorporate into the reactant mixture from which the 
matrix is formed a compound comprising at least one phosphorus-carbon or 
phosphorus-boron covalent bond such as boron phosphate. The compound 
preferably comprises at least one phosphonic acid group, or a salt 
thereof, in an amount effective in service to extend the working time of 
the composition. Preferably, the compound comprises a polybasic phosphonic 
acid. Particularly effective such compounds also comprise at least one 
other complexing group, suitably a hydroxyl or an amino, preferably a 
tertiary amino, group. It has been found that the materials sold under the 
trade mark "DEQUEST" ("DEQUEST" is a registered trade mark) are very 
suitable, especially: 
##STR1## 
It is particularly desirable that the compound is soluble in, and 
preferably completely miscible in, an aqueous solution of the Bronsted 
acid. 
In accordance with a further aspect of this invention it is often desirable 
to incorporate into the matrix-forming mix a further complexing agent 
soluble in an aqueous solution of the Bronsted acid. The complexing agent 
may comprise a fluoride ligand or, more preferably, a chelating agent. The 
chelating agent may comprise a plurality of carboxyl groups, for example 
aconitic, itaconic, maleic, mellitic or tricarballylic acid; it may also 
comprise at least one hydroxyl group. Particularly preferred such 
chelating agents comprise citric, malic or tartaric acid. A further 
suitable type of chelating agent comprises a multivalent metal chelate, 
for example a beta-diketone chelate, such as is formed by copper or zinc. 
Such chelating agents are suitably present in an amount up to 20% by 
weight, preferably 0.1% or 10% by weight, especially 3% to 8% by weight, 
based on the weight of Bronsted acid. 
This invention also comprises a process for fabricating a body as 
aforesaid, which process comprises mixing components which will form a 
solid matrix of electrical conductivy .gtoreq.10.sup.-6 mho cm.sup.-1 
together with an elemental metal, or an alloy thereof, as aforesaid; 
placing the mixture at a locus comprising a substrate surface which 
comprises corrodible material; and permitting the mixture to form a 
coherent protective layer of an anti-corrosion composition thereon. The 
mixture may be placed by brush coating it onto the locus or may be both 
mixed and placed by spray coating it onto the locus. The reactants may be 
spray coated consecutively or concurrently. Very suitable coatings have 
been prepared, using electrostatic spray guns ex Ransberg (UK) Ltd., 
Weybridge, Surrey by alternate spraying of, first, a pigment; for example 
of the composition: 
6 parts zinc oxide; 
6 parts zinc metal dust; 
0.7 parts manganese dioxide (electrolyte powder) 
and then a 25% by weight aqueous solution of polyacrylic acid ex Allied 
Colloids Ltd., Bradfor, W. Yorkshire. Adherent, hard, resistant coatings 
were produced in this manner. This invention further comprises a body 
whenever so fabricated. 
In accordance with this invention, there is also provided a dry, intimate 
mixture of a basic or amphoteric oxide or hydroxide and an elemental 
metal, or alloy thereof, having a standard electrode potential (E.sub.o) 
at 25.degree. C. less than -0.44 volt, especially when comprising a 
phosphorus-containing compound as aforesaid. Such mixtures may also 
comprise at least one dry homo- or copolymer or an unsaturated Bronsted 
acid; for example, freeze-dried poly(acrylic acid).

The invention will now be illustrated by the following Examples. 
EXAMPLE 1 
6 g of zinc oxide powder (PolyF powder ex Dentsply Ltd.); 2 g of zinc metal 
dust (average particle size 7.5.mu. ex Goodfellow Metals Ltd.); and 2 g 
distilled deionised water were first mixed by spatulation on a glass slab 
to form a fine paste. 2 g of a 40% by weight aqueous solution of 
polyacrylic acid (Versicol E7 ex Allied Colloids Ltd.) of viscosity 
average molecular weight 30,000 were then blended into the fine paste and 
the resulting paste was immediately applied with a 1" brush to a mild 
steel coupon 15 cm.times.10 cm. Within minutes the coating so formed was 
observed to have set to a matt light grey coherent layer on the steel 
substrate. 
EXAMPLE 2 
Example 1 was repeated save that 4 g of zinc metal dust; 2 g of water and 2 
g of the aqueous solution of polyacrylic acid were used. 
EXAMPLE 3 
2 g of zinc oxide powder (PolyF powder ex Dentsply Ltd.); 2 g of a zinc 
aluminosilicate glass having an average particle size of 10.mu. and the 
composition, expressed in parts by weight, of ZnO (233); SiO.sub.2 (206) 
and Al.sub.2 O.sub.3 (70); 0.3 g of manganese dioxide; 2 g of zinc metal 
dust as used in Example 1; and 2 g of distilled deionised water were first 
mixed by spatulation on a glass slab to form a fine paste. 3 g of a 40% by 
weight aqueous solution of polyacrylic acid as used in Example 1 were then 
blended, and the resulting blend applied, as in Example 1. 
EXAMPLE 4 
Example 1 was repeated with the following formulation: 
1 g willemite (average particle size less than 50.mu.); 
1 g zinc metal dust; 
1 g distilled deionised water; 
0.1 g manganese dioxide; 
1 g 40% by weight aqueous solution of polyacrylic acid. 
EXAMPLE 5 
Example 1 was repeated with the following formulation: 
1 g ZnO (PolyF powder ex Dentsply Ltd.); 
1 g zinc cermet powder (average particle size less than 45 .mu.m); 
1 g 40% by weight aqueous solution of polyacrylic acid. 
1 g distilled deionised water; 
0.1 g manganese oxide. 
The zinc cermet powder was prepared from a blend of zinc metal dust (ex 
Goodfellow Metals) and a fluoraluminosilicate powder having the 
composition, expressed in parts by weight, of SiO.sub.2 (100); Al.sub.2 
O.sub.3 (27.2) and CaF.sub.2 (100). (3.1 weight/weight ratio), made by 
compressing the blend into a disc and heating in vacuo at 400.degree. C. 
for 30 minutes. 
EXAMPLE 6 
Example 1 was repeated with the following formulation: 
6 g ZnO (PolyF powder); 
6 g zinc metal dust (7.5 .mu.m, Goodfellow Metals); 
2 g distilled deionised water; 
2 g 50% by weight aqueous solution of polymaleic acid (ex Polysciences Ltd; 
average molecular weight 1,000); 
0.7 manganese dioxide. 
The blend formed an adhesive coating with a good finish; no disbonding in 
3% NaCl solution was observed. 
EXAMPLE 7 
Example 6 was repeated with the following formulation: 
6 g ZnO (PolyF powder); 
6 g zinc metal dust (7.5 .mu.m, Goodfellow Metals); 
2 g distilled deionised water; 
2 g 50% by weight aqueous solution of copolymer of acrylic acid and 
itaconic acid (2:1 copolymer "Chembond" liquid ex Dentsply Ltd.); 
0.7 g manganese dioxide. 
The blend formed an adhesive coating with a good finish; no disbonding in 
3% NaCl solution was observed. 
EXAMPLE 8 
Example 6 was repeated with the following formulation: 
6 g ZnO (PolyF powder); 
6 g zinc metal dust (7.5 .mu.m, Goodfellow Metals Ltd.); 
2 g distilled deionised water; 
2 g 40% by weight aqueous solution of polymethacrylic acid (ex Polysciences 
Ltd.); 
0.7 g manganese dioxide. 
The blend formed an adhesive coating with a good finish; no disbonding in 
3% NaCl solution was observed. 
EXAMPLE 9 
Example 6 was repeated with the following formulation: 
3 g ZnO (PolyF powder); 
3 g Zn metal dust (Goodfellow Metals); 
1 g 50% by weight aqueous solution of mellitic acid (ex BDH); 
0.3 g manganese dioxide. 
The blend dried to a matt finish; non-adherent to mild steel. 
EXAMPLE 10 
6 g of zinc oxide powder (polyF powder ex Dentsply Ltd.); 6 g of zinc metal 
dust (average particle size 7.5.mu. ex Goodfellow Metals Ltd.); and 2 g 
distilled deionised water were first mixed by spatulation on a glass slab 
to form a fine paste. 2 g of a 40% by weight aqueous solution of 
polyacrylic acid (Versicol E7 ex Allied Colloids Ltd.) of viscosity 
average molecular weight 30,000 were then blended into the fine paste and 
the resulting paste was immediately applied with a 1' brush to a mild 
steel coupon 15 cm.times.10 cm. Within minutes the coating so formed was 
observed to have set to a matt light grey coherent layer on the steel 
substrate. 
EXAMPLE 11 
In this Example, coated substrated prepared as in Examples 1 and 10 were 
each separately immersed in large glass beakers in a 3% by weight solution 
of sodium chloride (AnalaR grade) in distilled water: (sea water averages 
approximately 3% by weight of sodium chloride). The electrical potential 
of the coated steel substrates was each separately measured, using a 
voltmeter (Keithley Model 169 Multimeter) with a very high impedance (at 
least 10 Mohm), against a saturated calomel electrode. A comparative 
coated substrate (steel coated with GALVAFROID) and a control (steel with 
no coating) were likewise tested. 
Measurements were regularly made over a test period of one month and it was 
found that in both samples where the substrate had been coated in 
accordance with this invention the electrical potential of the steel was 
less (greater negative value) than that in either the case of the 
comparative or the control samples. 
Visual inspection of the samples during the test period showed that the 
samples where the substrate had been coated in accordance with this 
invention had resisted the corrosive effects of the saline solution much 
more effectively: their surfaces were still matt grey and there was 
substantially less solid matter deposited in the glass beakers. 
EXAMPLE 12 
In this Example, coated substrates prepared as in Examples 1 to 10 but of 
the sizes 38 cm.times.25 cm and 30 cm.times.30 cm were subjected to field 
trials as MOD Portsmouth. Samples were tested by bolting to steel girder 
rigs mounted on shore (salt spray test) and at a sandbank (half tide 
test). Comparative samples coated with GALVAFROID were also tested. All 
samples were retrieved after 12 weeks. Visual inspection suggested that 
while both types of sample in both sites showed evidence of corrosion this 
was less pronounced where the substrate had been coated in accordance with 
this invention. Furthermore, where corrosion had occurred it was, in the 
case of substrates which had been coated in accordance with the invention, 
generally confined about striations which might have been the result of 
gross corrosion of the coating by solid matter dispersed in the sea water. 
In the case of the comparative samples corrosion was not so confined and 
was clearly much more pronounced. 
EXAMPLE 13 
In this Example, coated substrates prepared as in Examples 1 and 10 were 
subjected to a bend test (BS 3900 (Part E1)) using a 13 mm diameter 
cylindrical mandrel. In each case the samples passed the test. 
EXAMPLE 14 
A two component system of the following formulation was prepared: 
Component A 
6 g ZnO (PolyF powder) 
6 g Zn metal dust (average particle size 7.5.mu. ex Goodfellow Metals Ltd.) 
0.7 g MnO.sub.2 (electrolytic grade) 
2 g distilled deionised water 
Component B 
2 g "Chembond" liquid 
0.5 g DEQUEST 2000 (ex Monsanto Ltd.) 
Component A was blended together to form a paste which, in turn, was mixed 
with component B, at ambient temperature and humidity, by spatulation. A 
portion of the paste was then applied to a mild steel coupon as in Example 
1; the remainder was tested for working time. It was found that the paste 
had a working time of 6.5 minutes but required curing for 12 to 16 hours 
on the coupon to ensure complete resistance to a 3% aqueous sodium 
chloride solution. 
EXAMPLE 15 
Example 14 was repeated except that mixing was effected at 4.5.degree. C. 
and 50% RH, and the curing was effected for 24 hours. The working time of 
the resulting paste increased to 19 minutes. After 24 hours in a 3% 
aqueous sodium chloride solution at 4.5.degree. C. the coated coupon was 
found to suffer slight loss of material. 
EXAMPLE 16 
Example 14 was repeated except that mixing was effected at 25.degree. C. 
and 100% RH. The working time of the resulting paste was 11.25 minutes. 
After curing for 24 hours on the coupon the coating was found to be 
resistant to a 3% aqueous sodium chloride solution. No corrosion was 
observed during 5 days immersion of the coated coupon in the solution. 
EXAMPLE 17 
Example 14 was repeated except that 3 g of the zinc oxide was replaced by 3 
g of boron phosphate (ex Alfa Organics Ltd.). The working time of the 
resulting paste was 16.3 minutes. After curing for 24 hours on the coupon 
the coating was found to be resistant to a 3% aqueous sodium chloride 
solution. No corrosion was observed during 6 days immersion of the coated 
coupon in the solution. 
EXAMPLE 18 
Example 17 was repeated except that the boron phosphate was replaced by 3 g 
of brick dust (ex London Brick Co. Ltd.; No. 12 particle size &lt;45.mu.). 
The working time of the resulting paste was 4 minutes. After curing for 24 
hours on the coupon the coating was found to be resistant to a 3% aqueous 
sodium chloride solution. No corrosion was observed during 6 days 
immersion of the coated coupon in the solution. 
EXAMPLE 19 
A two component system of the following formulation was prepared: 
Component A 
5 g brick dust (ex London Brick Co. Ltd.; No. 12) 
6 g Zn metal dust (average particle size 7.5.mu. ex Goodfellow Metals Ltd.) 
0.7 g MnO.sub.2 (electrolytic) 
4 g distilled deionised water 
Component B 
2 g "Chembond" liquid 
Component A was blended together to form a paste which, in turn, was mixed 
with component B, at 23.+-.2.degree. C. and 50.+-.% RH, by spatulation. A 
portion of the paste was then applied to a mild steel coupon as in Example 
1; the remainder was tested for working time. It was found that the paste 
had a working time of 30 minutes but required curing for 24 hours on the 
coupon to ensure complete resistance to a 3% aqueous sodium chloride 
solution. 
EXAMPLE 20 
Example 19 was repeated except that component A additionally comprised 0.92 
g dry "Chembond" powder and component B comprised 5.08 g of water. The 
working time of the resulting paste was 5 minutes. 
EXAMPLE 21 
Example 17 was repeated except that the boron phosphate was replaced by 
calcined ferric oxide (ex BDH Ltd.). The working time of the resulting 
paste was 4 minutes. After curing for 24 hours on the coupon the coating 
was found to be resistant to a 3% aqueous sodium chloride solution. No 
corrosion was observed during 5 days immersion of the coated coupon in the 
solution. 
EXAMPLE 22 
A two component system of the following formulation was prepared: 
Component A 
5.6 g calcined Fe.sub.2 O.sub.3 (ex BDH Ltd.) 
Zn metal dust (average particle size 7.5.mu. ex Goodfellow Metals Ltd.) 
0.7 g MnO.sub.2 (electrolytic) 
4.0 g distilled deionised water 
Component B 
2 g "Chembond" liquid 
A paste was prepared from the components and tested as in Example 14. The 
working time of the resulting paste was 90 minutes. After curing for 24 
hours on the coupon the coating was found to be resistant to a 3% aqueous 
sodium chloride solution. No corrosion was observed during 14 days 
immersion of the coated coupon in the solution. 
EXAMPLE 23 
A two component system of the following formulation was prepared: 
Component A 
10.4 g micaceous Fe.sub.3 O.sub.4 (ex MIOX) 
6.0 g Zn metal dust (average particle size 7.5.mu. ex Goodfellow Metals 
Ltd.) 
4.0 g distilled deionised water 
Component B 
2 g "Chembond" liquid 
A paste was prepared from the components and tested as in Example 19. The 
working time of the resulting paste was 14 minutes. Slight corrosion was 
observed at the coupon edge after 7 days. 
EXAMPLE 24 
A two component system of the following formulation was prepared: 
Component A 
5.6 g calcined Fe.sub.2 O.sub.3 (ex BDH Ltd.) 
6.0 g Zn metal dust (average particle size 7.5.mu. ex Goodfellow Metals 
Ltd.) 
0.92 g solid poly(acrylic acid) (VERSICOL E7 M=30,000 ex Allied Colloids 
Ltd.) 
0.13 g borax (Fisons AR grade) 
0.10 g NaH.sub.2 PO.sub.4.2H.sub.2 O (Fisons AR grade) 
Component B 
5.08 g distilled deionised water 
A paste was prepared from the components and tested as in Example 19. The 
working time of the resulting paste was 34 minutes. After curing for 24 
hours on the coupon the coating was found to be resistant to a 3% aqueous 
sodium chloride solution. No corrosion was observed during 2 days 
immersion of the coated coupon in the solution. 
EXAMPLE 25 
Example 24 was repeated except that the borax and sodium dihydrogen 
phosphate was replaced by 0.23 g of boron phosphate. The working time of 
the resulting paste was 4.7 minutes. 
EXAMPLE 26 
Example 24 was repeated except that the borax and sodium dihydrogen 
phosphate was replaced by 0.23 g of boric acid. The working time of the 
resulting paste was 5.25 minutes. 
EXAMPLE 27 
Example 24 was repeated except that 0.23 g of borax was used and the sodium 
dihydrogen phosphate was omitted. The working time of the resulting paste 
was 8.50 minutes. 
EXAMPLE 28 
Example 24 was repeated except that 0.23 g of sodium dihydrogen phosphate 
dihydrate was used and the borax was omitted. The working time of the 
resulting paste was 44 minutes. After curing for 24 hours on the coupon 
the coating was found to be resistant to a 3% aqueous sodium chloride 
solution. 
EXAMPLES 29 TO 35 
A two component system of the following formulation was prepared: 
Component A 
5.6 g calcined Fe.sub.2 O.sub.3 (ex BDH Ltd.) 
6.0 g Zn metal dust (average particle size 7.5.mu. ex Goodfellow Metals 
Ltd.) 
0.2 g MnO.sub.2 (electrolyte) 
4.0 g distilled deionised water 
Component B 
2.0 g of the polyacid shown in Table 1, the amount taken being such that 
the quantities of acid and of water in the formulations were the same in 
each example. 
A paste was prepared from the components and tested as in Example 14. The 
working time and corrosion resistance of coupons coated with the paste and 
determined after curing for 24 hours on the coupon are shown in Table 1. 
TABLE 1 
______________________________________ 
Example Working Performance in 
No. Acid Time 3% NaCl solution 
______________________________________ 
29 Chembond 34 Stable; no corrosion 
over 17 days 
30 50% PAA.sup.1 ; --M = 
31 Stable; waterline 
5,000 (ex Aldrich) discolouration after 
17 days 
31 25% PAA; --M = 
5.3 Cracking and blister- 
90,000 (ex Aldrich) ing after 24 hours 
32 Versicol E7 10 Blistering after 4 days 
immersion 
33 Versicol E9.sup.2 
6.25 Unworkable 
34 Poly F 10.5 No corrosion after 17 
days 
35 Versicol E5.sup.3 
15.5 Waterline discoloura- 
tion after 17 days 
______________________________________ 
.sup.1 poly(acrylic acid) 
.sup.2 --M = 75,000 
.sup.3 --M = 3,500 
EXAMPLES 36 TO 40 
A two component system of the following formulation was prepared: 
Component A 
5.6 g calcined Fe.sub.2 O.sub.3 (ex BDH Ltd.) 
6.0 g Zn metal dust (average particle size 7.5.mu. ex Goodfellow Metals 
Ltd.) 
0.7 g MnO.sub.2 (electrolytic) 
0.92 g dry polyacid powder (see Table 2) 
0.23 g Na H.sub.2 PO.sub.4.2H.sub.2 O 
Component B 
5.08 g distilled deionised water 
A paste was prepared from the components and tested as in Example 14. The 
working time and corrosion resistance of coupons coated with the paste and 
determined after curing for 24 hours on the coupon are shown in Table 2. 
TABLE 2 
______________________________________ 
Example Working Performance in 37% 
No. Acid time NaCl solution 
______________________________________ 
36 Chembond 83 Slight corrosion after 2 days 
37 Versicol E5 
70 " 
38 Versicol E7 
66 Slight corrosion after 6 days 
39 Versicol E9 
37.5 Good resistance over 6 days 
40 Poly F 41 " 
______________________________________ 
EXAMPLES 41 TO 45 
Example 29 was repeated except that the given zinc powder was replaced by 
that shown in Table 3 which also shows the working time and corrosion 
resistance of coupons coated with the paste and determined after curing 
the 24 hours on the coupon. 
TABLE 3 
______________________________________ 
Example Working Performance in 
No. Zinc Time 3% NaCl solution 
______________________________________ 
41 ex BDH Ltd. A.R. 
12.75 Stable; no corrosion 
grade over 17 days 
42 ex Hopkins and 
4.75 Stable; no corrosion 
Williams L.R. over 20 days 
grade 
43 6 to 9.mu. ex ISC 
33 Slight corrosion after 
Alloys 16 days 
44 4.5 to 6.mu. ex 
10.5 Slight corrosion after 
ISC Alloys 16 days 
45 2.5.mu. ex Durham 
8 No corrosion over 4 
Chemicals days 
______________________________________ 
EXAMPLES 46 TO 50 
Example 36 was repeated except that the sodium dihydrogen phosphate was 
replaced by the additive shown in Table 4 which also shows the working 
time and corrosion resistance of the coupons coated with the paste and 
determined after curing for 24 hours on the coupon. 
TABLE 4 
______________________________________ 
Example Working Performance in 
No. Additive Time 3% NaCl Solution 
______________________________________ 
46 Dequest 2000.sup.x 
92 Local attack at water- 
line after 5 days 
47 Dequest 2010.sup.x 
59 Local attack at water- 
line after 5 days 
48 Dequest 2060.sup.x 
88 No corrosion over 6 
days 
49 Sodium tripoly- 
45 Slight attack after 
phosphate (ex Alfa) 6 days 
50 Na.sub.3 PO.sub.4.12H.sub.2 O 
48 Slight attack after 
(ex Fisons) 6 days 
______________________________________ 
.sup.x 0.46 g as 50 m/m solutions 
EXAMPLES 51 TO 53 
Example 36 was repeated except that the acid used throughout was dried 
Versicol E7 and that the given zinc powder was replaced by the additive 
shown in Table 5 which also shows the working time and corrosion 
resistance of coupons coated with the paste and determined after curing 
for 24 hours on the coupon. 
TABLE 5 
______________________________________ 
Example Working Performance in 
No. Zinc powder Time 3% NaCl Solution 
______________________________________ 
51 ISC alloys:SP 
50 Stable; attack at 
waterline after 12 days 
52 8.mu. ex Durham 
43 Stable; attack at 
Chemicals waterline after 12 days 
53 6.mu. ex Durham 
29 Stable; spot corrosion 
Chemicals at waterline after 
12 days 
______________________________________ 
EXAMPLES 54 AND 55 
Example 51 was repeated except that the sodium dihydrogen phosphate was 
replaced by the additive shown in Table 6 which also shows the working 
time and corrosion resistance of coupons coated with the paste and 
determined after curing for 24 hours on the coupon. 
TABLE 6 
______________________________________ 
Example Working Performance in 
No. Additive Time 3% NaCl Solution 
______________________________________ 
54 0.46 g 50% M/M 
29 Slight discolouration 
Dequest 2060.sup.x above waterline after 
21 days 
55 0.46 g 50% gly- 
13 Corrosion at waterline 
cerophosphoric at 21 days 
acid (ex T. Morson) 
______________________________________ 
.sup.x 4.85 g of water was added in each case 
EXAMPLES 56 TO 65 
Example 38 was repeated except that the zinc metal dust used was ISC SP and 
that chelating acids, added as solids at 5% m/m of the Versicol E7, were 
added as shown in Table 7 which also shows the working time and corrosion 
resistance of coupons coated with the paste and determined after curing 
for 24 hours on the coupon. 
TABLE 7 
______________________________________ 
Example 
Chelating Working Performance in 3% NaCl 
No. Acid Time Solution after 15 Days 
______________________________________ 
56 D(+) tartaric 
60 No apparent corrosion 
57 meso-tartaric 
52 Trace of white deposit 
58 maleic 47 Spot corrosion 
59 succinic 52 Corrosion apparent 
60 diglycolic 70 Some corrosion at waterline 
61 ketomalonic 
51 Corrosion at waterline 
62 citric 63 Slight corrosion at waterline 
63 oxalic 61 Corroded 
64 glycolic 65 Corroded 
65 mesaconic 58 Some corrosion 
______________________________________ 
EXAMPLE 66 
A two component system of the following formulation was prepared: 
Component A 
6 g zinc oxide (Poly F) 
6 g zinc powder (average particle size 7.5.mu. ex Goodfellow Metals Ltd.) 
0.7 g MnO.sub.2 (electrolytic) 
2.0 g distilled deionised water 
Component B 
2 g 40% Versicol E7 
50% m/m Dequest solutions shown in Table 8 which also shows the working 
time and corrosion resistance of coupons coated with the paste and 
determined after curing for 24 hours on the coupon. 
TABLE 8 
______________________________________ 
Working Setting 
Amount Time Time Stability in Water 
Dequest 
Added (min) (min) After Setting 
______________________________________ 
2000 0.5 g 3.25 12 Good 
1.0 g 13.75 ca. 60 Poor 
1.5 g 24.75 ca. 90 Too viscous to apply 
2060 0.5 g &lt;2 &lt;4 -- 
1.0 g 2.5 4.25 Good 
1.5 g 8.5 20 Slight solubility 
2.0 g 23.25 50 Poor 
______________________________________ 
The Example was effected under ambient conditions of temperature and 
relative humidity. 
EXAMPLE 67 
Example 56 was repeated except that component B comprises 3.82 g distilled 
water and 2.54 g of ca. 50% m/m dispension of a rubber which comprises a 
carboxylated styrene-butadiene copolymer (ex Enichem Elastomer Ltd.). 
Results are as follows: 
______________________________________ 
Performance in 
3% NaCl solution 
Rubber 3 mm mandrel bend test 
after 16 days 
(Intex) 
on tin-free steel substrate 
mild steel substrate 
______________________________________ 
166 No cracking: 25% could be 
No corrosion 
scraped off the bent region. 
178 Slight cracking: 50% could be 
Slight corrosion at 
scraped off the bent region. 
waterline 
1478 No cracking. Very small 
Slight corrosion 
amount could be scraped off 
the bent region. 
1493 No cracking: 75% detached 
Slight corrosion 
on scraping from the bent 
region. 
______________________________________ 
EXAMPLE 68 
Component A 
3 g Zinc metal dust (ex ISC Alloys:SP) 
0.46 g Poly(acrylic acid) (Versicol E7:solid) 
Component B 
1 g H.sub.2 O 
Pot life 25 minutes. 
EXAMPLE 69 
Component A 
3 g Zinc metal dust (average particle size 7.mu. ex Goodfellow Metals Ltd.) 
0.46 g Poly(acrylic acid) Versicol E7:solid) 
Component B 
1 g H.sub.2 O 
Pot life 25 minutes. 
EXAMPLE 70 
Component A 
3 g Zinc metal dust (average particle size 7.mu. ex Goodfellow Metals Ltd.) 
1 g Chembond 
Component B 
0.54 g H.sub.2 O 
Pot life 25 minutes. 
EXAMPLE 71 
Component A 
3 g Zinc metal dust (ex ISC Allys:SP) 
0.46 g Poly(acrylic acid) Versicol E7:solid) 
0.35 g Manganese dioxide (electrolytic) 
Component B 
1 g H.sub.2 O 
Pot life 13 minutes. 
The amount of water used in formulating Examples 68 to 71 inclusive was 
lower than that in the other filled systems because of the lower solids. 
The pot life of all the coatings was sufficient for good quality brush 
coatings to be prepared.