Use of yttrium, zirconium, lanthanum, cerium, praseodymium and/or neodymium as reinforcing agent for an anticorrosion coating composition

The subject of the invention is therefore the use of at least one element selected from yttrium, zirconium, lanthanum, cerium, praseodymium, and neodymium in the form of oxides and salts as a means to enhance the anticorrosive properties of the anticorrosive coating composition containing metal particles in the aqueous or organic phase for metal parts.

A further object of the invention is the use of at least one of the aforementioned elements, optionally associated with Mo0 molybdenum oxide₃as a means to enhance the anticorrosive properties of the anticorrosive coating composition containing metal in the form of particles in the aqueous or organic phase for metal parts.

It seems, without restrictive interpretation, that the presence of at least one of the above-mentioned elements makes it possible to strengthen the effectiveness of corrosion protection provided by metal in the form of particles in the composition.

The metal in the form of particles present in the composition is preferably added in the form of a powder with different geometrical, homogeneous and heterogeneous structure, especially in spherical, lamellar, lenticular and other specific forms.

Oxides or salts of the above-mentioned elements, which are used as agents that enhance the anticorrosive properties of the compositions, are usually in the form of powder, the particles of which have₅₀ less than 20 pm (value of D₅₀ means that 50% of the number of particles have a particle size smaller than this value, and 50% of the number of particles have a particle size larger than this value). When preparing the coating composition, it is possible to carry out prior comminution of the particles or a dispersion step (to break up the agglomerates into elementary particles) so that the composition contains particles having a D value₅₀ less than 3 pm.

These oxides or salts may be completely soluble, partly soluble or completely insoluble in the aqueous phase or organic phase. They can be in dispersed or dissolved form in the composition.

Yttrium salts are preferably selected from acetate, chloride, formate, carbonate, sulfamate, lactate, nitrate, oxalate, sulfate, yttrium phosphate or aluminate (Y₃Al₅Oi₂), and mixtures thereof.

Yttrium oxide is preferably in the form Y₂ABOUT₃.

Yttrium is preferably used in the form of an oxide.

Yttrium oxide Y₂ABOUT₃ used to prepare the coating composition is generally in the form of particles having a size in the range between 1 pm and 40 pm, with a D.50 value of approximately 6 to 8 pm. When preparing the coating composition, it is possible to carry out a prior grinding of the particles or a dispersion stage (to break up the agglomerates into elementary particles) so that the composition contains particles having D_?,_fi less than 3 pm.

Zirconium salts are preferably selected from zirconium carbonate, silicate, sulfate and titanate, and mixtures thereof.

Zirconium is preferably in the form of ZrO₂.

The lanthanum salts are preferably selected from acetate, oxalate, nitrate, sulfate, carbonate, phosphate, and lanthanum aluminate (LaAlO₃), and mixtures thereof.

Lanthanum oxide is preferably in the form of La₂ABOUT₃.

The cerium salts are preferably selected from chloride, carbonate, acetate, nitrate, oxalate, sulfate, phosphate, cerium molybdate (Ce₂ (M0O4) 3) and cerium tungstate (Ce₂(WO₄)₃) and their mixtures.

The cerium oxide is preferably in the form of CeO₂.

Cerium is preferably used in the form of cerium chloride or CeO₂.

The praseodymium salts are preferably selected from praseodymium carbonate, chloride, nitrate, oxalate, and sulfate, and mixtures thereof.

The praseodymium oxide is preferably in the form of Pr₆0n.

Neodymium salts are preferably selected from neodymium carbonate, chloride, nitrate, and sulfate, and mixtures thereof.

Neodymium oxide is preferably in the form of Nd₂ABOUT₃.

In case the composition also contains molybdenum oxide

Mo0₃, associated with one of the above-mentioned elements used as a reinforcing agent of the anticorrosive properties of the composition, M0O3 is preferably incorporated in a substantially pure rhombic crystalline form and has a molybdenum content greater than about 60% by weight.

Preferably, the molybdenum oxide M0O3 is in the form of particles having a size between 1 pm and 200 pm.

Preferably, said anticorrosion enhancer of the composition is associated with molybdenum oxide M0O3 in a weight ratio of 0.25 <anticorrosion enhancer: M0O3 <20, preferably 0.5 <anticorrosion enhancer: Mo0₃<16, more preferably 0.5 <anti-corrosive agent: MoO₃ < 14.

It contains in particular 0.5% to 2% by weight Mo0₃.

Preferably Yttria Y₂ABOUT₃ is used in the form associated with molybdenum oxide M0O3. Another object of the invention is the use of Y-oxide₂ABOUT₃ in the form associated with molybdenum oxide M0O3 in a weight ratio of 0.25 <Y₂0₃: Mo0₃ <20, preferably 0.5 <Y₂0₃: Mo03 <16, more preferably 0.5 <Y₂0₃: Mo03 <14.

A further subject of the invention are anti-corrosive coating compositions for metal parts comprising:

- at least one metal in the form of particles,

- anticorrosive agent enhancing the composition selected from yttrium, zirconium, lanthanum, cerium, praseodymium and neodymium, in the form of oxides or salts, optionally associated with molybdenum oxide M0O3,

- binding agent, and

- either water, optionally associated with one or more organic solvents, or one or more miscible organic solvents.

The coating composition contains at least one particle metal, i.e. one or more particles metal.

Preferably, the metal content in the form of particles is in the range between 10% and 40% by weight based on the weight of the composition.

The particulate metal may be selected from zinc, aluminum, tin, manganese, nickel, their alloys, and mixtures thereof.

Preferably, the particulate metal is selected from zinc, aluminum, their alloys and mixtures thereof. Preferably, the alloys are selected from zinc and aluminum alloys containing at least 3% by weight aluminum, preferably 7% by weight aluminum and zinc and tin alloys containing at least 10% by weight tin.

The content of the anticorrosive agent of the composition is in the range between 0.5% and 10% by weight based on the weight of the composition, preferably between 1% and 8% by weight based on the weight of the composition, more preferably between 1% and 7% based on composition weight.

The anticorrosion enhancer of the composition is preferably yttrium, preferably in the form of Y oxide₂ABOUT₃ or yttrium carbonate or cerium preferably in the form of cerium chloride or CeO oxide₂.

In addition, the reinforcing agent may be selected from La₂ABOUT_3/ pr₆0n, Sun₂ABOUT₃ and ZrO₂.

The anticorrosion enhancer of the composition is preferably associated with MoO molybdenum oxide₃ in a weight ratio of 0.25 <anti-corrosion agent: Mo0₃ <20, preferably 0.5 <anti-corrosive agent: Mo0₃ <16, more preferably 0.5 <anti-corrosive agent: Mo0₃ < 14.

The binder content preferably ranges between 3% and 20% by weight based on the weight of the mixture. The binder may be of the organic and / or mineral type, in the aqueous or organic phase. The choice of binder depends on various criteria, including the firing temperature of the coating composition.

The binder is preferably selected from an alkoxylated silane, optionally with an introduced organic functional group, such as γ-glycidoxypropyltrimethoxysilane and γ-glycidoxypropyltriethoxysilane, silicone resin, colloidal silica, sodium silicate and / or potassium silicate and / or lithium silicate, zirconate, polyoxyethane acrylic compound and mixtures thereof.

The binder may be associated with a phenolic type, aminoplast type or dicyandiamide type crosslinker. Acid catalysts may also be added to catalyze the crosslinking reaction.

When the composition is in the aqueous phase, colloidal silica associated with the resins can be used as the binder.

When the coating composition is in the aqueous phase, the liquid phase is formed of water and may also contain up to 30% by weight of an organic solvent or a mixture of water-miscible organic solvents.

When the coating composition is in the organic phase, the liquid phase is entirely formed of an organic solvent or a mixture of organic solvents miscible with each other.

The solvent or organic solvents are selected with respect to the binder so that they dissolve the binder or stabilize its dispersion. Preferably the organic solvent or solvents are selected from white spirit, alcohols, ketones, aromatic solvents, and glycol solvents such as glycol ethers, especially diethylene glycol, triethylene glycol and dipropylene glycol, acetates, polyethylene glycol and nitropropane, and mixtures thereof.

The coating composition may also contain a thickener if the type of application so requires, for example if it is to be applied by immersion centrifugation.

The thickener content is preferably up to 7% by weight based on the weight of the composition, preferably between 0.005% and 7% by weight based on the weight of the composition.

Preferably, the thickener is selected from cellulose derivatives such as hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, or hydroxypropyl methyl cellulose, xanthan gum, associative polyurethane or acrylic thickeners, silicates, silicates such as magnesium silicates and / or lithium silicates, optionally treated with lithium or and mixtures thereof.

The coating composition may also contain a lubricant in an amount sufficient to provide a self-lubricating system, selected in particular from polyethylene, polytetrafluoroethylene, MoS₂, graphite, polysulfones, synthetic or natural waxes and nitrides, and mixtures thereof.

The coating composition, if it is in the aqueous phase, may also contain other additives compatible with the binder, selected from an antifoaming agent such as Schweg foam (emulsified hydrocarbon) from Schwegman, a wetting agent such as ethoxylated monylphenol or polyethylene ethoxylate, a surfactant, such as Aerosol TR 70 (sodium sulfosuccinate) from Cytec and a biocide such as Ecocide D75 from Progiva, and a weak acid, such as boric acid to regulate the pH of the composition.

Preferably, the coating composition includes the following components:

10% to 40% by weight of at least one metal in the form of particles,

- 0.5% to 10% by weight of an agent improving the corrosion protection properties of the composition selected from yttrium, zirconium, lanthanum, cerium, praseodymium and neodymium, in the form of oxides or salts, optionally associated with MoO molybdenum oxide₃,

- up to 7% by weight of a thickener,

- 3% to 20% by weight of a binder, up to 3% by weight, preferably 0.05% to 2% by weight of sodium silicate and / or potassium silicate and / or lithium silicate,

- up to 7% by weight of one or more lubricants,

1% to 30% by weight of an organic solvent or mixture of organic solvents,

<td>optional 0.1%</td><td>down</td><td>10% by weight weak</td><td>acid</td>

<td>mineral like</td><td>acid</td><td>boric,</td><td></td>

<td>optional 0.01%</td><td>down</td><td>1% by weight anionic</td><td>agent</td>

surfactant, and

- water to make up to 100%.

If the abovementioned anticorrosion enhancer is associated with molybdenum oxide, the latter preferably comprises 0.5% to 2% by weight of the composition.

Of course, the present invention also extends to anti-corrosive coatings applied to metal parts using the above-mentioned compositions.

Application can be carried out by spraying, draining on immersion or centrifuging on immersion, whereby the coating layer is then subjected to an oven-firing operation (e.g. convection or infrared) preferably carried out convectionally at a temperature between 70 ° C and 350 ° C for 10 up to 60 minutes.

According to one preferred embodiment, the anti-corrosive coating is from an application operation comprising, prior to the firing operation, an operation for drying coated metal parts (e.g. by convection or infrared), especially by convection at a temperature in the region of 70 ° C for approximately 10 to 30 minutes he rope.

Under these conditions, the thickness of the dry film thus applied is in the range between 3 pm (11 g / m2)²) and 15 pm (55 g / m2²), preferably between 4 pm (15 g / m2²) and 10 pm (40 g / m2)²), more preferably between 5 pm (18 g / m2²) and 10 pm (40 g / m2)²) .

The present invention also extends to a metal substrate, preferably steel, provided with an anti-corrosive coating applied using the above-mentioned compositions.

It itself can be coated with another coating to further strengthen some properties, such as corrosion protection or lubrication. The coating for reinforcing corrosion protection may contain alkali silicate, especially sodium and / or potassium and / or lithium silicate, acrylic compound, zirconate, titanate, silane, epoxy resin, phenolic resin or one of their mixtures, these resins being optionally associated with colloidal silica. The coating for lubrication may comprise a lubricant selected from polyethylene, polytetrafluoroethylene, MoS_from, graphite, polysulfones, synthetic and natural waxes and nitrides and mixtures thereof.

Corrosion tests

A) Effect of yttrium oxide (Y2O3) in the aqueous phase, optionally associated with molybdenum oxide (Mo0₃) for corrosion protection.

Comparative experiments were conducted on the coating compositions given in Table 1.

Table 1

<td rowspan="2">% by weight</td><td colspan="4">composition</td>

<td> 1</td><td> 2</td><td> 3</td><td> 4</td>

<td>Y2O3¹</td><td> 0</td><td> 3, 0</td><td> 0</td><td> 3, 0</td>

<td>M0O3</td><td> 0</td><td> 0</td><td> 0, 9</td><td> 0,9</td>

<td>Zinc²</td><td colspan="4"> 23, 6</td>

<td>Aluminum³</td><td colspan="4"> 3,0</td>

<td>Silane A 187⁴</td><td colspan="4"> 10, 1</td>

<td>Sodium silicate 20N32⁵</td><td colspan="4"> 0,9</td>

<td>Rempcopal®N4 10O⁶</td><td colspan="4"> 1,4</td>

<td>Rempcopal®N9 100⁷</td><td> 1, 6</td>

<td>glycol dipropylene</td><td> 7,5</td>

<td>Aerosil® 380⁸</td><td> &lt;0, 1</td>

<td>Schwego® foam 8325⁹</td><td> 0,5</td>

<td>Boric acid</td><td> 0, 8</td>

<td>Water deionized</td><td>up to 100%</td>

^ΧΥ₂Ο₃ ο 99.99% purity (Rhodia) ²Zinc in paste form, approximately 92% in white spirit (80% Alu Stapa PG Chromał VIII, from Eckart Werke) ³Aluminum, approximately 80% in dipropylene glycol, ⁴Y-glycidoxypropyltrimethoxysilane (Crompton) ⁵ Sodium Silicate (Rhodia) ⁶ Nonylphenol ethoxylated wetting agent (Uniąema) ⁷ Nonylphenol ethoxylated wetting agent (Uniąema) ⁸ Silica anti-sedimentation agent (Degussa) ⁹ Antifoaming hydrocarbon type.

Prepared samples

Worked surface: degreased, shot blasted steel screws

Application of the coating composition: immersion centrifugation

Firing: 25 min. at 310 ° C

Coating layer weight: 26 ± 2 g / m2²

Steel bolts machined in this way were tested by salt spraying in accordance with NFISO 9227. The results of salt spray resistance are given in Table 2.

Table 2

<td>Composition</td><td>s₂about₃(% by weight)</td><td>Mo0₃(% by weight)</td><td>Resistance to salt spraying (number of hours)</td>

<td> 1</td><td> 0</td><td> 0</td><td> 140-260</td>

<td> 2</td><td> 3</td><td> 0</td><td> 840</td>

<td> 3</td><td> 0</td><td> 0,9</td><td> 500</td>

<td> 4</td><td> 3</td><td> 0,9</td><td> 1300</td>

Table 2 clearly shows that the addition of Y-oxide₂ABOUT₃ for coating compositions increases the salt spray resistance of samples treated with such compositions.

In addition, when yttrium oxide Y₂ABOUT₃ is associated with MoO molybdenum oxide₃, corrosion protection is further improved. The interaction or synergy effect between Y is observed₂ABOUT₃ and MoO₃, which strengthens the anticorrosive effect of the composition.

B) Effect of zinc alloy with 7% aluminum (Stapa Zn₄Al₇ from Eckkart

Werke) for corrosion protection.

Comparative experiments were conducted on the coating compositions given in Table 3.

Table 3

<td>composition</td><td></td>

<td> 5</td><td>Identical to composition number 3</td>

<td> 6</td><td>Identical to composition number 4</td>

<td> 7</td><td>Identical to composition number 4 except that 30% by weight of zinc is replaced by a zinc alloy with 7% by weight of aluminum (Zn alloy Zn₄Al₇ from Eckart Werke).</td>

Prepared samples:

Worked surface: degreased, shot blasted steel screws

Application of the coating composition: immersion centrifugation

Firing: 25 min. at 310 ° C

Coating layer weight: 26 ± 2 g / m2¹

The steel bolts were treated with the coating compositions of Table 3, then tested by salt spraying in accordance with NFISO 9227.

Salt spray resistance results are given in Table 4.

Table 4

<td>Composition</td><td>Y2O3 (% by weight)</td><td>M0O3 (% by weight)</td><td>treading Al-Zn ^ z / n (% by weight)</td><td>Resistance to spraying salt (number hours)</td>

<td> 5</td><td> 0</td><td> 0, 9</td><td> 0</td><td> 450</td>

<td> 6</td><td> 3</td><td> 0, 9</td><td> 0</td><td> 1370</td>

<td> 7</td><td> 3</td><td> 0, 9</td><td> 30</td><td> 1900</td>

Table 4 shows that the anticorrosive effect of the composition is better for zinc alloy than for zinc.

C) Effect of cerium chloride in the water phase on corrosion protection

Comparative experiments were conducted on the coating compositions given in Table 5.

Table 5

<td>composition</td><td></td>

<td> 8</td><td>Identical to composition number 3</td>

<td> 9</td><td>Identical to composition number 1 except that that 0.5 wt.% cerium chloride is additionally added to other ingredients</td>

<td> 10</td><td>Identical to composition number 1 except that that 2% by weight cerium chloride is additionally added to other ingredients</td>

Prepared samples

Worked surface: degreased, shot blasted steel screws

Application of the coating composition: immersion centrifugation

- Firing: 25 min. at 310 ° C

- Weight of the coating layer: 26 + 2 g / m2²

The steel bolts were treated with the coating compositions of Table 5, then tested by salt spraying in accordance with NFISO 9227.

Salt spray resistance results are given in the table

6.

Table 6

<td>composition</td><td>Cerium chloride (% by weight)</td><td>Resistance to salt spraying (number of hours)</td>

<td> 8</td><td> 0</td><td> 200</td>

<td> 9</td><td> 0,5</td><td> 500</td>

<td> 10</td><td> 2</td><td> 770</td>

Table 6 clearly shows that the addition of cerium chloride to coating compositions increases the salt spray resistance of samples treated with such compositions.

D) Effect of yttrium carbonate in the water phase on corrosion protection

Comparative experiments were conducted on the coating compositions given in Table 7.

Table 7

<td>Composition</td><td></td>

<td> 11</td><td>Identical to composition number 1</td>

<td> 12</td><td>Identical to composition number 3 except that 0.8% by weight of the composition M0O3 instead of 0.9%</td>

<td> 13</td><td>Identical to composition number 2 except that that 3% by weight of Y₂ABOUT₃ replaced by 6.9% by weight of yttrium carbonate</td>

<td> 14</td><td>Identical to composition number 4 except that that 3% by weight of Y₂ABOUT₃ replaced by 6.9% by weight of yttrium carbonate and is found in the composition 0.8 wt% MoO₃ instead of 0.9%</td>

Steel bolts were prepared, machined and tested as in Example 1. The results of salt spray resistance are given in Table 8.

Table 8

<td>composition</td><td>Carbonate yttrium (% by weight)</td><td>Mo0₃(% by weight)</td><td>Spray resistance salt (number of hours)</td>

<td> 11</td><td> 0</td><td> 0</td><td> 288</td>

<td> 12</td><td> 0</td><td> 0, 8</td><td> 400</td>

<td> 13</td><td> 6,9</td><td> 0</td><td> 288</td>

<td> 14</td><td> 6, 9</td><td> 0, 8</td><td> 1296</td>

Table 8 clearly shows that when yttrium carbonate is associated with molybdenum oxide M0O3, the anti-corrosive effect is improved. The interaction or synergy effect between yttrium carbonate and is observed

M0O3, which strengthens the anticorrosive effect of the composition.

E) Effect of various oxides in the aqueous phase on corrosion protection

Comparative experiments were conducted on the coating compositions given in Table 9.

Table 9

<td>Composition</td><td></td>

<td> 15</td><td>Identical to composition number 1</td>

<td> 16</td><td>Identical to composition number 3</td>

<td> 17</td><td>Identical to composition number 2</td>

<td> 18</td><td>Identical to composition number 4</td>

<td> 19</td><td>Identical to composition number 2 except that that Y₂ABOUT₃ is provided by Sogemet</td>

<td> 20</td><td>Identical to composition number 4 except that that Y2O3 is provided by Sogemet</td>

<td> 21</td><td>Identical to composition number 2 except that that Y₂ABOUT₃ is replaced by CeO₂ supplied through Rhodia</td>

<td> 22</td><td>Identical to composition number 4 except that that Y2O3 is replaced by CeO₂ supplied through Rhodia</td>

<td> 23</td><td>Identical to composition number 2 except that that Y₂ABOUT₃ is replaced by CeO₂ supplied by Sogemet</td>

<td> 24</td><td>Identical to composition number 4 except that that Y₂ABOUT₃ is replaced by CeO₂ supplied by Sogemet</td>

<td> 25</td><td>Identical to composition number 2 with the difference that Y₂ABOUT₃ is replaced by La₂ABOUT₃ supplied through Rhodia</td>

<td> 26</td><td>Identical to composition number 4 except that that Y₂ABOUT₃ is replaced by La₂ABOUT₃ supplied through Rhodia</td>

<td> 27</td><td>Identical to composition number 2 except that that Y₂ABOUT₃ is replaced by La₂ABOUT₃ supplied by Sogemet</td>

<td> 28</td><td>Identical to composition number 4 except that that Y₂0₃ is replaced by La₂ABOUT₃ supplied by Sogemet</td>

<td> 29</td><td>Identical to composition number 2 except that that Y₂ABOUT₃ is replaced by Pr₆ABOUT₁₂</td>

<td> 30</td><td>Identical to composition number 4 except that that Y₂0₃ is replaced by Pr₆0u</td>

<td> 31</td><td>Identical to composition number 2 except that that Y₂0₃ is replaced by Nd₂ABOUT₃</td>

<td> 32</td><td>Identical to composition number 4 except that that Y2O3 is replaced by Nd₂ABOUT₃</td>

<td> 33</td><td>Identical to composition number 2 except that that Y₂0₃ is replaced by ZrO₂</td>

<td> 34</td><td>Identical to composition number 4 except that that Y₂ABOUT₃ is replaced by ZrO₂</td>

El) Electrochemistry

Treated substrates: degreased and sandblasted steel plates,

- Application of the coating composition: using a hand-held coating device

Firing: 25 min. at 310 ° C

Coating layer weight: 26 ± 2 g / m '

Polarization resistance of the coatings was measured during one hour with the SOLARTRON 1250 (Schlumberger) analyzer, in the air, with a scanning index of ± 10mV at 0, 1mV xs^_1. The results of these measurements are given in Table 10. The higher the polarization resistance value, the better the predicted anticorrosive effect of the coatings.

Table 10

<td>Composition</td><td>Oxide</td><td>Oxide (% by weight)</td><td>MoO₃(% by weight)</td><td>Resistance to polarity (Ω x cm²)</td>

<td> 15</td><td></td><td> 0</td><td> 0</td><td> 3300</td>

<td> 16</td><td></td><td> 0</td><td> 0, 9</td><td> 9100</td>

<td> 17</td><td>^ 2θ3 Rhodia</td><td> 3</td><td> 0</td><td>don't mark</td>

<td> 18</td><td>Y / O₃ Rhodia</td><td> 3</td><td> 0, 9</td><td> 12100</td>

<td> 21</td><td>CeO₂ Rhodia</td><td> 3</td><td> 0</td><td> 10600</td>

<td> 22</td><td>CeO₃ Rhodia</td><td> 3</td><td> 0, 9</td><td> 12000</td>

<td> 23</td><td>CeO₂ Sogemet</td><td> 3</td><td> 0</td><td> 10000</td>

<td> 24</td><td>CSO₂ Sogemet</td><td> 3</td><td> 0, 9</td><td> 12000</td>

<td> 25</td><td>La₃ABOUT₃ Rhodia</td><td> 3</td><td> 0</td><td>don't mark</td>

<td> 26</td><td>Ώ &amp; 2θ3 Rhodia</td><td> 3</td><td> 0, 9</td><td> 11900</td>

<td> 27</td><td>LĆI2O3 Sogemet</td><td> 3</td><td> 0</td><td> 9300</td>

<td> 28</td><td>L3.2O3 Soqemet</td><td> 3</td><td> 0, 9</td><td> 10100</td>

<td> 29</td><td>pr₆0 and 1</td><td> 3</td><td> 0</td><td> 9900</td>

<td> 30</td><td>pr₆ABOUT_at</td><td> 3</td><td> 0, 9</td><td> 9800</td>

<td> 31</td><td>Nd₂ABOUT₃</td><td> 3</td><td> 0</td><td> 9400</td>

<td> 32</td><td>Nd₂ABOUT₃</td><td> 3</td><td> 0, 9</td><td> 10000</td>

<td> 33</td><td>ZrO₂</td><td> 3</td><td> 0</td><td> 9200</td>

<td> 34</td><td>ZrO₂</td><td> 3</td><td> 0,9</td><td> 12000</td>

Table 10 clearly shows that the addition of yttrium, cerium, lanthanum, praseodymium, neodymium or zirconium oxide to the coating compositions increases the polarization resistance of the coatings, indicating that the corrosion resistance of these coatings is likely to be increased.

E-2) Corrosion resistance.

Steel bolts were prepared, machined and tested as in Example 1. The results of salt spray resistance are given in Table 11.

Table 11

<td>Composition</td><td>Oxide</td><td>Oxide (% by weight)</td><td>Mo0₃(% by weight)</td><td>Resistance to spraying salt (number hours)</td>

<td> 15</td><td></td><td> 0</td><td> 0</td><td> 288</td>

<td> 16</td><td> —</td><td> 0</td><td> 0,9</td><td> 400</td>

<td> 17</td><td>Υ₂Ο₃Rhodi a</td><td> 3</td><td> 0</td><td> 1056</td>

<td> 18</td><td>s₂about₃Rhodia</td><td> 3</td><td> 0,9</td><td> &gt;1500</td>

<td> 19</td><td>Y₂ABOUT₃Sogemet</td><td> 3</td><td> 0</td><td> 1296</td>

<td> 20</td><td>Y₂ABOUT₃Sogemet</td><td> 3</td><td> 0, 9</td><td> &gt;1656</td>

<td> 21</td><td>CeO₂Rhodia</td><td> 3</td><td> 0</td><td> 144</td>

<td> 22</td><td>CeO₂Rhodia</td><td> 3</td><td> 0,9</td><td> 720</td>

<td> 23</td><td>CSO2 Sogemet</td><td> 3</td><td> 0</td><td> 144</td>

<td> 24</td><td>CeO₂Sogemet</td><td> 3</td><td> 0, 9</td><td> 792</td>

<td> 25</td><td>LS2O3 Rhodia</td><td> 3</td><td> 0</td><td> 336</td>

<td> 26</td><td>La₂ABOUT₃Rhodi a</td><td> 3</td><td> 0,9</td><td> 552</td>

<td> 27</td><td>L1 &amp; 2O3 Sogemet</td><td> 3</td><td> 0</td><td> 552</td>

<td> 28</td><td>La₂ABOUT₃Sogemet</td><td> 3</td><td> 0, 9</td><td> 864</td>

<td> 29</td><td>On Pr ^</td><td> 3</td><td> 0</td><td> 504</td>

<td> 30</td><td>PrgOn</td><td> 3</td><td> 0, 9</td><td> 864</td>

<td> 31</td><td>Nd₂ABOUT₃</td><td> 3</td><td> 0</td><td> 288</td>

<td> 32</td><td>Nd₂ABOUT₃</td><td> 3</td><td> 0, 9</td><td> 1560</td>

<td> 33</td><td>ZrO₂</td><td> 3</td><td> 0</td><td> 288</td>

<td> 34</td><td>ZrO₂</td><td> 3</td><td> 0,9</td><td> 456</td>

Table 11 clearly shows that the addition of yttrium, lanthanum, praseodymium, neodymium or zirconium oxide to coating compositions increases the spray resistance of salts treated with these compositions. The best oxide appears to be Y₂ABOUT₃, but Neodynium, Praseodynium and Lanthanum also give good results.

In addition, when the oxide is associated with molybdenum oxide M0O3, the anti-corrosive effect is further improved. The interaction between oxide and M0O3 is observed, which reinforces the anticorrosive effect of the composition.

DACRAL

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80P21094PL00

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