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anticorrosive pigments containing coatings
ARTICLE IN PRESS
Journal of Physics and Chemistry of Solids 68 (2007) 1101–1105 www.elsevier.com/locate/jpcs
Electrochemical, chemical and barrier action of zinc dust/anticorrosive pigments containing coatings J. Havlı´ k, A. Kalendova´, D. Vesely´ Department of Paints and Organic Coatings, Institute of Polymeric Materials, Faculty of Chemical-technology, University of Pardubice, na´m. Cˇs. legiı´ 565, 53210 Pardubice, Czech Republic
Abstract This work deals with the study of anticorrosive efficiency of coatings containing a combination of zinc dust and non-metallic pigments. Eight non-metallic anticorrosive pigments combined with zinc dust VM 4P16 were used. For each combination of pigments were prepared three or four types of epoxyester coatings with different pigment volume concentration. All coatings were pigmented to a degree of Q ¼ 65%. The effectiveness of these systems was rated according to the resistance of the coatings exposed to 5% salt spray in a saltspray cabinet with NaCl solution and humidity condensation and to SO2 atmosphere in a humidity cabinet. The obtained results were analyzed by subjective evaluation methods. r 2006 Published by Elsevier Ltd. Keywords: A. Anticorrosive pigment; A. Zinc powder; D. Anticorrosive efficiency
1. Introduction Corrosion protection has been a very important issue lately. Designing of novel coating systems consisting of pigments with their characteristic properties, suitable binder, fillers and additives, appears to be crucial. It is important to bear in mind high anticorrosive action of entire coating system and environmental-friendly behaviour at the same time. Zinc dust particles have been used for many years as efficient anticorrosive pigment in heavy-duty coatings. Principle, by which zinc particles act in coatings is based on assumption of creating so-called ‘‘scalling effects’’ and on consequent electrochemical processes. The process is called ‘‘cathodic protection’’ and once corrosive process has begun, zinc starts to behave as anodic side. Anticorrosive pigments termed ‘‘chemically active’’ are to a certain extend soluble. They contain soluble ingredients that may keep constant pH value in a coating layer. These pigments are called ‘‘active’’ and their effect depends on their reaction at phase boundaries, interfaces between Corresponding author.
E-mail address: [email protected] (J. Havlı´ k). 0022-3697/$ - see front matter r 2006 Published by Elsevier Ltd. doi:10.1016/j.jpcs.2006.11.016
pigment and substrate and between a binder and pigment, respectively. They may react with ions that penetrate within an organic coating as well. It is advantageous to combine both inhibitor types in a single formulation, which results in decrease of Zn dust in the coating by retaining constant anticorrosive efficiency [1,2].
2. Experimental 2.1. Types of the testing pigments Inorganic compounds, which are well known and are widely used for effective anticorrosive properties, were chosen to be put through investigation. They differ in amount of containing cations and anions, which participate on electrochemical processes. Pigments based on phosphates, borates, chromates and other modified compounds, which possess in their structure cations of Zn, Ca and Mo are best performing. For the investigation of the anticorrosive action spineltype pigments were chosen. Spinels are compounds posing crystal lattice consisted of 32 oxygen ions. In between each of two oxygen ions there are incorporated cations of
ARTICLE IN PRESS J. Havlı´k et al. / Journal of Physics and Chemistry of Solids 68 (2007) 1101–1105
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material tested. To gain the spinel crystal lattice stable, the ion diameters and their ratios do not have to exceed certain, energetically and space-limited values [3,4,5]. The mixed pigment oxides containing cations of Ca, Zn, Mg, Ti that possess spinel structure of 4-2 type were synthesized. Perowskit CaTiO3 and pigments containing Ca, Zn, Mg of spinel type 3-2 were synthesized in a laboratory scale as well. The pigments used are summarized in Table 1. 2.2. Pigments tested characteristics For the particular pigments the following properties were measured: density, oil consumption, water soluble particles content, pH of water leach, conductivity and X-ray structure analysis as well (Figs. 1 and 2). Table 1 Summary of the pigments used
2.3. Coatings formulations Mixtures of Zn dust and a particular pigment were incorporated within resin based on epoxyester by using the model formulations. All the coatings posed equal value of PVC/CPVC at 0.65 (Q ¼ 65%). The values of PVC were set at 0%, 10%, 20%, and 30%, when the amount of zinc powder was calculated from the Q ¼ 65%. Furthermore, coatings containing just pure pigments by their individual CPVC were prepared. Beside these, coatings pigmented with zinc powder together with inert pigment (TiO2 AV 01) and coatings pigmented with a combination of zinc powder and physically acting pigment (CaSiO3) were prepared. Then coatings containing pure zinc powder at a level of 0%, 10%, 20%, 30% and CPVC value were prepared. Finally, nonpigmented coating a reference one was prepared as well. 2.4. Specimens preparation
Pigment
Pigment
Zn3(PO4)2 4H2O Ca(BO2)2 K2CrO4 3ZnCrO4 Zn(OH)2 2H2O CaSiO3 Zn2TiO4 Mg2TiO4 CaTiO3
TiO2 ZnFe2O4 MgFe2O4 CaFe2O4 Mg0.5Ca0.5Fe2O4 Zn0.5Mg0.5Fe2O4 Zn0.5Ca0.5Fe2O4
Model formulations of coatings based on epoxyester binder were prepared in order to test the anticorrosive properties of the pigments under investigation. Particular coatings were prepared using zinc powder and pigments, which differ in chemical composition, their morphologies and total anticorrosive action. The preparation was carried out using Dispermat Disolver, dispersion time of 15 min and rotations of 1500 RPM. In order to avoid the particles settlement and better dispersion, 0.15 wt% of rheological additive Bentone SD-1 was used. 2.5. The coatings applying The coatings were applied on steel panels (150 10 0.9 mm). Before applying, organic impurities from the panels were washed off with acetone and chloroform. On so-prepared surface the coatings were applied using applying ruler with a hole of 250 mm. Once the first layer was totally dry, the procedure repeated using a ruler with a hole of 200 mm. Drying of the coatings was carried out at the ambient temperature.
Fig. 1. Mg0.5Ca0.5Fe2O4 particle.
2.6. Salt-spray chamber cyclic test The test specimens (panels with the coatings) were put through the salt-spray test (test with a scratch located in the middle of the specimens). The dry film thickness was measured by magnetic thickness meter according to the ISO 2808. The total anticorrosive efficiency was obtained by the creeps assessment according to the ASTM D 1654-92, substrate evaluation (ASTM D 610) and a degree of coatings’ blistering (ASTM D 1654-92). The calculation of the total anticorrosive efficiency for the salt-spray chamber tests is given in the following equation:
Fig. 2. Zn0.5Ca0.5Fe2O4 particle.
A¼
A1 þ A2 þ A3 , 3
ARTICLE IN PRESS J. Havlı´k et al. / Journal of Physics and Chemistry of Solids 68 (2007) 1101–1105
where A, total anticorrosive efficiency; A1, a value of blistering; A2, a degree of substrate degradation; and A3, a value is the creep evaluation. 3. Results and discussion 3.1. Salt-spray chamber cyclic test Test principle is based on changing of exposure of the samples to the NaCl (5 wt% NaCl) by 35 1C for 6 h, exposure to humidity by 40 1C for 4 h and a consequent drying by 23 1C for 2 h. All the samples under investigation were cyclically tested for 1500 h. The degree of blistering according to the ASTM D 714-87 standard was evaluated in fixed periods while exposed. The total exposure period was chosen to generate sufficient differences in the anticorrosive efficiencies. It was proven that the coatings pigmented with Zn dust showed comparable results compared with the coatings pigmented with the commercially available pigments. The total anticorrosive efficiency dropped away by decreased amount of the pigments contained, except of K2CrO4 3ZnCrO4 Zn(OH)2 2H2O. The coatings pigmented with the K2CrO4 3ZnCrO4 Zn(OH)2 2H2O by the CPVC showed the best anticorrosive efficiency. The results are given in Table 2. The coatings pigmented with a mixture of Zn dust and TiO2-based pigments showed the best anticorrosive effi-
1103
ciency, particularly for the Mg2TiO4/Zn pigmented specimen. On contrary, the worst total anticorrosive efficiency was, if the coatings were pigmented at the value of CPVC. Separate results are summarized in Table 3. Results of the total anticorrosive efficiencies of the coatings pigmented with Zn dust and mixed metal oxides pigments are given in Tables 4 and 5, respectively. From the osmotic blistering standpoint, the best efficiency showed the specimens pigmented with the combination of Zn dust and K2CrO4 3ZnCrO4 Zn(OH)2 2H2O, K2CrO4 3ZnCrO4 Zn(OH)2 2H2O by the CPVC value and CaFe2O4/Zn. The worst efficiency was found on the specimen pigmented with CaTiO3 by the CPVC. All the coatings pigmented at the CPVC value showed low antiblistering efficiency, except of the specimen pigmented with ZnFe2O4 and MgFe2O4. Majority of the specimen substrates were free of defects. On contrary, the zero resistance against the substrate corrosion was found if the coatings were pigmented with Ca(BO2)2, CaSiO3, CaTiO3 by CPVC and the coatings pigmented with Mg0.5Ca0.5Fe2O4, Zn0.5Mg0.5Fe2O4 and Zn0.5Ca0.5Fe2O4. 4. Conclusion The coatings pigmented with MgFe2O4, K2CrO4 3ZnCrO4 Zn(OH)2 2H2O, ZnFe2O4 by CPVC showed
Table 2 Evaluation of the salt-spray chamber performance (Zn dust/commercially available pigments) PVC (% of pigment)
Dry film thickness (mm)
Blistering (ASTM)
Zn3(PO4)2 4H2O+Zn 10 20 30
90 93.8 112.7
— — —
Zn3(PO4)2 4H2O CPVC
104.7
6MD
Ca(BO2)2+Zn 10 20 30 Ca(BO2)2 CPVC
94.9 87.2 88.3 113
K2CrO4 3ZnCrO4 Zn(OH)2 2H2O+Zn 10 90.6 20 84.8
— — 6F 4MD
Substrate corrosion (ASTM)
0.01 0.01 0.01 33 0.01 0.03 0.1 100
— —
0.01 0.01
K2CrO4 3ZnCrO4 Zn(OH)2 2H2O (SNCZ CZ 20) CPVC 81.6 —
0.01
CaSiO3+Zn 10 20 30
0.3 0.1 0.1
CaSiO3 CPVC
88.1 71.8 99.6
6M — —
110.1
4M
100
Creep (ASTM)
Total anticorrosive efficiency
0.5–1 1–2 1–2
93 90 90
0.5–1
43
0.5–1 0.5–1 1–2
93 93 78
—
35
0.5–1 0.5–1
93 93
0–0.5 0 0.5–1 0.5–1 0–0.5
97 80 92 92 45
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Table 3 Evaluation of the salt-spray chamber performance (Zn dust/TiO2-based pigments) PVC (% of pigment)
Dry film thickness (mm)
Blistering (ASTM)
Substrate corrosion (ASTM)
Zn2TiO4+Zn 10 20 30
84.1 70.8 82.2
— 8D 4MD
0.01 10 3
3–5 1–2 1–2
83 48 55
Zn2TiO4 CPVC
58.3
8M
10
1–2
62
Mg2TiO4+Zn 10 20
59.4 82.1
— —
0.5–1 0–0.5
93 97
Mg2TiO4 CPVC
68.4
4MD
0.5–1
55
CaTiO3+Zn 10 20 30
96.3 80.7 62.3
— — —
0.5–1 0.5–1 1–2
93 93 90
CaTiO3 CPVC
63.4
2D
TiO2+Zn 10 20 30
95.6 81.1 94.1
— 8D 2M
TiO2 CPVC
81.1
2MD
0.01 0.01 10 0.01 0.01 0.01 100 0.01 0.03 0.1 100
Creep (ASTM)
Total anticorrosive efficiency
0–0.5
30
1–2 1–2 1–2
90 62 68
0–0.5
37
Table 4 Evaluation of the salt-spray chamber performance (combination of Zn dust and mixed metal oxides pigments) PVC (% of pigment)
Dry film thickness (mm)
Blistering (ASTM)
ZnFe2O4+Zn 10 20
67.2 75.1
6M 8F
ZnFe2O4 CPVC
84.8
MgFe2O4+Zn 10 20
Creep (ASTM)
Total anticorrosive efficiency
0.1 0.01
0–0.5 0.5–1
78 85
—
0.01
0–0.5
97
77.3 64.9
— 4F
0.01 0.01
0.5–1 0–0.5
93 85
MgFe2O4 CPVC
47.8
—
0.03
0–0.5
97
CaFe2O4+Zn 10 20
86.9 89.2
— —
0.03 0.01
0–0.5 0.5–1
97 93
CaFe2O4 CPVC
88.8
8M
0–0.5
55
the best total anticorrosive efficiency as well as the coatings pigmented with Zn/Mg2TiO4 (PVC ¼ 20%), Zn/CaFe2O4 (PVC ¼ 10%) and Zn/Mg0.5Ca0.5Fe2O4 (PVC ¼ 10%, 30%). On contrary, the worst total
Substrate corrosion (ASTM)
33
anticorrosive performance was found on the specimens pigmented with Ca(BO2)2, TiO2, CaSiO3, Zn0.5 Mg0.5Fe2O4, Mg0.5Ca0.5Fe2O4 and Zn0.5Ca0.5Fe2O4 by CPVC.
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Table 5 Evaluation of the salt-spray chamber performance (combination of Zn dust and mixed metal oxides pigments) PVC (% of pigment)
Dry film thickness (mm)
Blistering (ASTM)
Substrate corrosion (ASTM)
Creep (ASTM)
Total anticorrosive efficiency
Mg0.5Ca0.5Fe2O4+Zn 10 20 30
81.8 66.1 67.3
— 4F —
0.01 1 0.03
0–0.5 0.5–1 0–0.5
97 75 97
Mg0.5Ca0.5Fe2O4 CPVC
55.9
2MD
100
0–0.5
37
Zn0.5Mg0.5Fe2O4+Zn 10 20
67.2 52.8
6F 4F
0.01 0.03
0–0.5 0–0.5
87 85
Zn0.5Mg0.5Fe2O4 CPVC
59.1
4D
100
0.5–1
28
Zn0.5Ca0.5Fe2O4+Zn 10 20
79.9 85.9
6F 6F
0.01 0.01
0.5–1 0–0.5
83 87
Zn0.5Ca0.5Fe2O4 CPVC
62.1
6MD
100
0–0.5
40
Acknowledgement This work was supported by the Ministry of Education of Czech Republic under project MSM 0021627501. References [1] A. Kalendova´, V. Cˇechalova´, P. Prokesˇ , Affecting the anticorrosion efficiency of zinc-pigmented coatings by the combination with nonmetal pigment particles, Acta Mech. Slovaca 9 (3) (2005) 99–104.
[2] A. Kalendova´, Effects of particle sizes and shapes of zinc powder on the properties of anticorrosive coatings, Prog. Organ. Coatings 46 (4) (2003) 324–332. [3] A. Kalendova´, P. Kalenda, Influencing the anticorrosion efficiency of zinc-pigmented coatings by means of lamellar pigments, Pitture Vernici Eur. Coatings 79 (8) (2003) 51–53. [4] A. Kalendova´, Comparison of the anticorrosion efficiencies of pigments based on condensed phosphates and polyphosphosilicates, Anti-Corrosion Methods 50 (2) (2003) 82–90. [5] A. Kalendova´, J. Brodinova´, Spinel and rutile pigments containing Mg, Ca, Z and other cations for anticorrosive coatings, AntiCorrosion Methos Mater. 50 (5) (2003) 352–363.
Journal of Physics and Chemistry of Solids 68 (2007) 1101–1105 www.elsevier.com/locate/jpcs
Electrochemical, chemical and barrier action of zinc dust/anticorrosive pigments containing coatings J. Havlı´ k, A. Kalendova´, D. Vesely´ Department of Paints and Organic Coatings, Institute of Polymeric Materials, Faculty of Chemical-technology, University of Pardubice, na´m. Cˇs. legiı´ 565, 53210 Pardubice, Czech Republic
Abstract This work deals with the study of anticorrosive efficiency of coatings containing a combination of zinc dust and non-metallic pigments. Eight non-metallic anticorrosive pigments combined with zinc dust VM 4P16 were used. For each combination of pigments were prepared three or four types of epoxyester coatings with different pigment volume concentration. All coatings were pigmented to a degree of Q ¼ 65%. The effectiveness of these systems was rated according to the resistance of the coatings exposed to 5% salt spray in a saltspray cabinet with NaCl solution and humidity condensation and to SO2 atmosphere in a humidity cabinet. The obtained results were analyzed by subjective evaluation methods. r 2006 Published by Elsevier Ltd. Keywords: A. Anticorrosive pigment; A. Zinc powder; D. Anticorrosive efficiency
1. Introduction Corrosion protection has been a very important issue lately. Designing of novel coating systems consisting of pigments with their characteristic properties, suitable binder, fillers and additives, appears to be crucial. It is important to bear in mind high anticorrosive action of entire coating system and environmental-friendly behaviour at the same time. Zinc dust particles have been used for many years as efficient anticorrosive pigment in heavy-duty coatings. Principle, by which zinc particles act in coatings is based on assumption of creating so-called ‘‘scalling effects’’ and on consequent electrochemical processes. The process is called ‘‘cathodic protection’’ and once corrosive process has begun, zinc starts to behave as anodic side. Anticorrosive pigments termed ‘‘chemically active’’ are to a certain extend soluble. They contain soluble ingredients that may keep constant pH value in a coating layer. These pigments are called ‘‘active’’ and their effect depends on their reaction at phase boundaries, interfaces between Corresponding author.
E-mail address: [email protected] (J. Havlı´ k). 0022-3697/$ - see front matter r 2006 Published by Elsevier Ltd. doi:10.1016/j.jpcs.2006.11.016
pigment and substrate and between a binder and pigment, respectively. They may react with ions that penetrate within an organic coating as well. It is advantageous to combine both inhibitor types in a single formulation, which results in decrease of Zn dust in the coating by retaining constant anticorrosive efficiency [1,2].
2. Experimental 2.1. Types of the testing pigments Inorganic compounds, which are well known and are widely used for effective anticorrosive properties, were chosen to be put through investigation. They differ in amount of containing cations and anions, which participate on electrochemical processes. Pigments based on phosphates, borates, chromates and other modified compounds, which possess in their structure cations of Zn, Ca and Mo are best performing. For the investigation of the anticorrosive action spineltype pigments were chosen. Spinels are compounds posing crystal lattice consisted of 32 oxygen ions. In between each of two oxygen ions there are incorporated cations of
ARTICLE IN PRESS J. Havlı´k et al. / Journal of Physics and Chemistry of Solids 68 (2007) 1101–1105
1102
material tested. To gain the spinel crystal lattice stable, the ion diameters and their ratios do not have to exceed certain, energetically and space-limited values [3,4,5]. The mixed pigment oxides containing cations of Ca, Zn, Mg, Ti that possess spinel structure of 4-2 type were synthesized. Perowskit CaTiO3 and pigments containing Ca, Zn, Mg of spinel type 3-2 were synthesized in a laboratory scale as well. The pigments used are summarized in Table 1. 2.2. Pigments tested characteristics For the particular pigments the following properties were measured: density, oil consumption, water soluble particles content, pH of water leach, conductivity and X-ray structure analysis as well (Figs. 1 and 2). Table 1 Summary of the pigments used
2.3. Coatings formulations Mixtures of Zn dust and a particular pigment were incorporated within resin based on epoxyester by using the model formulations. All the coatings posed equal value of PVC/CPVC at 0.65 (Q ¼ 65%). The values of PVC were set at 0%, 10%, 20%, and 30%, when the amount of zinc powder was calculated from the Q ¼ 65%. Furthermore, coatings containing just pure pigments by their individual CPVC were prepared. Beside these, coatings pigmented with zinc powder together with inert pigment (TiO2 AV 01) and coatings pigmented with a combination of zinc powder and physically acting pigment (CaSiO3) were prepared. Then coatings containing pure zinc powder at a level of 0%, 10%, 20%, 30% and CPVC value were prepared. Finally, nonpigmented coating a reference one was prepared as well. 2.4. Specimens preparation
Pigment
Pigment
Zn3(PO4)2 4H2O Ca(BO2)2 K2CrO4 3ZnCrO4 Zn(OH)2 2H2O CaSiO3 Zn2TiO4 Mg2TiO4 CaTiO3
TiO2 ZnFe2O4 MgFe2O4 CaFe2O4 Mg0.5Ca0.5Fe2O4 Zn0.5Mg0.5Fe2O4 Zn0.5Ca0.5Fe2O4
Model formulations of coatings based on epoxyester binder were prepared in order to test the anticorrosive properties of the pigments under investigation. Particular coatings were prepared using zinc powder and pigments, which differ in chemical composition, their morphologies and total anticorrosive action. The preparation was carried out using Dispermat Disolver, dispersion time of 15 min and rotations of 1500 RPM. In order to avoid the particles settlement and better dispersion, 0.15 wt% of rheological additive Bentone SD-1 was used. 2.5. The coatings applying The coatings were applied on steel panels (150 10 0.9 mm). Before applying, organic impurities from the panels were washed off with acetone and chloroform. On so-prepared surface the coatings were applied using applying ruler with a hole of 250 mm. Once the first layer was totally dry, the procedure repeated using a ruler with a hole of 200 mm. Drying of the coatings was carried out at the ambient temperature.
Fig. 1. Mg0.5Ca0.5Fe2O4 particle.
2.6. Salt-spray chamber cyclic test The test specimens (panels with the coatings) were put through the salt-spray test (test with a scratch located in the middle of the specimens). The dry film thickness was measured by magnetic thickness meter according to the ISO 2808. The total anticorrosive efficiency was obtained by the creeps assessment according to the ASTM D 1654-92, substrate evaluation (ASTM D 610) and a degree of coatings’ blistering (ASTM D 1654-92). The calculation of the total anticorrosive efficiency for the salt-spray chamber tests is given in the following equation:
Fig. 2. Zn0.5Ca0.5Fe2O4 particle.
A¼
A1 þ A2 þ A3 , 3
ARTICLE IN PRESS J. Havlı´k et al. / Journal of Physics and Chemistry of Solids 68 (2007) 1101–1105
where A, total anticorrosive efficiency; A1, a value of blistering; A2, a degree of substrate degradation; and A3, a value is the creep evaluation. 3. Results and discussion 3.1. Salt-spray chamber cyclic test Test principle is based on changing of exposure of the samples to the NaCl (5 wt% NaCl) by 35 1C for 6 h, exposure to humidity by 40 1C for 4 h and a consequent drying by 23 1C for 2 h. All the samples under investigation were cyclically tested for 1500 h. The degree of blistering according to the ASTM D 714-87 standard was evaluated in fixed periods while exposed. The total exposure period was chosen to generate sufficient differences in the anticorrosive efficiencies. It was proven that the coatings pigmented with Zn dust showed comparable results compared with the coatings pigmented with the commercially available pigments. The total anticorrosive efficiency dropped away by decreased amount of the pigments contained, except of K2CrO4 3ZnCrO4 Zn(OH)2 2H2O. The coatings pigmented with the K2CrO4 3ZnCrO4 Zn(OH)2 2H2O by the CPVC showed the best anticorrosive efficiency. The results are given in Table 2. The coatings pigmented with a mixture of Zn dust and TiO2-based pigments showed the best anticorrosive effi-
1103
ciency, particularly for the Mg2TiO4/Zn pigmented specimen. On contrary, the worst total anticorrosive efficiency was, if the coatings were pigmented at the value of CPVC. Separate results are summarized in Table 3. Results of the total anticorrosive efficiencies of the coatings pigmented with Zn dust and mixed metal oxides pigments are given in Tables 4 and 5, respectively. From the osmotic blistering standpoint, the best efficiency showed the specimens pigmented with the combination of Zn dust and K2CrO4 3ZnCrO4 Zn(OH)2 2H2O, K2CrO4 3ZnCrO4 Zn(OH)2 2H2O by the CPVC value and CaFe2O4/Zn. The worst efficiency was found on the specimen pigmented with CaTiO3 by the CPVC. All the coatings pigmented at the CPVC value showed low antiblistering efficiency, except of the specimen pigmented with ZnFe2O4 and MgFe2O4. Majority of the specimen substrates were free of defects. On contrary, the zero resistance against the substrate corrosion was found if the coatings were pigmented with Ca(BO2)2, CaSiO3, CaTiO3 by CPVC and the coatings pigmented with Mg0.5Ca0.5Fe2O4, Zn0.5Mg0.5Fe2O4 and Zn0.5Ca0.5Fe2O4. 4. Conclusion The coatings pigmented with MgFe2O4, K2CrO4 3ZnCrO4 Zn(OH)2 2H2O, ZnFe2O4 by CPVC showed
Table 2 Evaluation of the salt-spray chamber performance (Zn dust/commercially available pigments) PVC (% of pigment)
Dry film thickness (mm)
Blistering (ASTM)
Zn3(PO4)2 4H2O+Zn 10 20 30
90 93.8 112.7
— — —
Zn3(PO4)2 4H2O CPVC
104.7
6MD
Ca(BO2)2+Zn 10 20 30 Ca(BO2)2 CPVC
94.9 87.2 88.3 113
K2CrO4 3ZnCrO4 Zn(OH)2 2H2O+Zn 10 90.6 20 84.8
— — 6F 4MD
Substrate corrosion (ASTM)
0.01 0.01 0.01 33 0.01 0.03 0.1 100
— —
0.01 0.01
K2CrO4 3ZnCrO4 Zn(OH)2 2H2O (SNCZ CZ 20) CPVC 81.6 —
0.01
CaSiO3+Zn 10 20 30
0.3 0.1 0.1
CaSiO3 CPVC
88.1 71.8 99.6
6M — —
110.1
4M
100
Creep (ASTM)
Total anticorrosive efficiency
0.5–1 1–2 1–2
93 90 90
0.5–1
43
0.5–1 0.5–1 1–2
93 93 78
—
35
0.5–1 0.5–1
93 93
0–0.5 0 0.5–1 0.5–1 0–0.5
97 80 92 92 45
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Table 3 Evaluation of the salt-spray chamber performance (Zn dust/TiO2-based pigments) PVC (% of pigment)
Dry film thickness (mm)
Blistering (ASTM)
Substrate corrosion (ASTM)
Zn2TiO4+Zn 10 20 30
84.1 70.8 82.2
— 8D 4MD
0.01 10 3
3–5 1–2 1–2
83 48 55
Zn2TiO4 CPVC
58.3
8M
10
1–2
62
Mg2TiO4+Zn 10 20
59.4 82.1
— —
0.5–1 0–0.5
93 97
Mg2TiO4 CPVC
68.4
4MD
0.5–1
55
CaTiO3+Zn 10 20 30
96.3 80.7 62.3
— — —
0.5–1 0.5–1 1–2
93 93 90
CaTiO3 CPVC
63.4
2D
TiO2+Zn 10 20 30
95.6 81.1 94.1
— 8D 2M
TiO2 CPVC
81.1
2MD
0.01 0.01 10 0.01 0.01 0.01 100 0.01 0.03 0.1 100
Creep (ASTM)
Total anticorrosive efficiency
0–0.5
30
1–2 1–2 1–2
90 62 68
0–0.5
37
Table 4 Evaluation of the salt-spray chamber performance (combination of Zn dust and mixed metal oxides pigments) PVC (% of pigment)
Dry film thickness (mm)
Blistering (ASTM)
ZnFe2O4+Zn 10 20
67.2 75.1
6M 8F
ZnFe2O4 CPVC
84.8
MgFe2O4+Zn 10 20
Creep (ASTM)
Total anticorrosive efficiency
0.1 0.01
0–0.5 0.5–1
78 85
—
0.01
0–0.5
97
77.3 64.9
— 4F
0.01 0.01
0.5–1 0–0.5
93 85
MgFe2O4 CPVC
47.8
—
0.03
0–0.5
97
CaFe2O4+Zn 10 20
86.9 89.2
— —
0.03 0.01
0–0.5 0.5–1
97 93
CaFe2O4 CPVC
88.8
8M
0–0.5
55
the best total anticorrosive efficiency as well as the coatings pigmented with Zn/Mg2TiO4 (PVC ¼ 20%), Zn/CaFe2O4 (PVC ¼ 10%) and Zn/Mg0.5Ca0.5Fe2O4 (PVC ¼ 10%, 30%). On contrary, the worst total
Substrate corrosion (ASTM)
33
anticorrosive performance was found on the specimens pigmented with Ca(BO2)2, TiO2, CaSiO3, Zn0.5 Mg0.5Fe2O4, Mg0.5Ca0.5Fe2O4 and Zn0.5Ca0.5Fe2O4 by CPVC.
ARTICLE IN PRESS J. Havlı´k et al. / Journal of Physics and Chemistry of Solids 68 (2007) 1101–1105
1105
Table 5 Evaluation of the salt-spray chamber performance (combination of Zn dust and mixed metal oxides pigments) PVC (% of pigment)
Dry film thickness (mm)
Blistering (ASTM)
Substrate corrosion (ASTM)
Creep (ASTM)
Total anticorrosive efficiency
Mg0.5Ca0.5Fe2O4+Zn 10 20 30
81.8 66.1 67.3
— 4F —
0.01 1 0.03
0–0.5 0.5–1 0–0.5
97 75 97
Mg0.5Ca0.5Fe2O4 CPVC
55.9
2MD
100
0–0.5
37
Zn0.5Mg0.5Fe2O4+Zn 10 20
67.2 52.8
6F 4F
0.01 0.03
0–0.5 0–0.5
87 85
Zn0.5Mg0.5Fe2O4 CPVC
59.1
4D
100
0.5–1
28
Zn0.5Ca0.5Fe2O4+Zn 10 20
79.9 85.9
6F 6F
0.01 0.01
0.5–1 0–0.5
83 87
Zn0.5Ca0.5Fe2O4 CPVC
62.1
6MD
100
0–0.5
40
Acknowledgement This work was supported by the Ministry of Education of Czech Republic under project MSM 0021627501. References [1] A. Kalendova´, V. Cˇechalova´, P. Prokesˇ , Affecting the anticorrosion efficiency of zinc-pigmented coatings by the combination with nonmetal pigment particles, Acta Mech. Slovaca 9 (3) (2005) 99–104.
[2] A. Kalendova´, Effects of particle sizes and shapes of zinc powder on the properties of anticorrosive coatings, Prog. Organ. Coatings 46 (4) (2003) 324–332. [3] A. Kalendova´, P. Kalenda, Influencing the anticorrosion efficiency of zinc-pigmented coatings by means of lamellar pigments, Pitture Vernici Eur. Coatings 79 (8) (2003) 51–53. [4] A. Kalendova´, Comparison of the anticorrosion efficiencies of pigments based on condensed phosphates and polyphosphosilicates, Anti-Corrosion Methods 50 (2) (2003) 82–90. [5] A. Kalendova´, J. Brodinova´, Spinel and rutile pigments containing Mg, Ca, Z and other cations for anticorrosive coatings, AntiCorrosion Methos Mater. 50 (5) (2003) 352–363.