T 2552/11 (Anticorrosive metallic coatings/NOF) 14-04-2015

Reasons for the Decision

1. The appeal is admissible.

2. Oral submissions by the accompanying person

2.1 The appellant announced in its letter dated 18 March 2015 that "Dr. Christoph Jeworrek will give a statement in court as an expert for chemistry. He will refer to the prior art documents cited by the opponent".

The appellant did not provide any evidence indicating that Mr. Jeworrek met the requirements of Article 133 EPC to represent the appellant, nor could his name be found in the list of professional representatives before the EPO.

During the oral proceedings of 14 April 2015 the respondent requested that Mr. Jeworrek not be heard. It emphasised that the appellant had not specified on what subject Mr. Jeworrek was supposed to speak.

2.2 According to decision G 04/95 (OJ EPO 1996, 412), oral submissions by an accompanying person are not a matter of right, but are subject to the permission and discretion of the EPO (see point (3)(a) of the order).

The criteria to be considered by the EPO when exercising this discretion are specified in this decision as follows (see point (3) of the order):

"(i) The professional representative should request permission for such oral submissions to be made. The request should state the name and qualifications of the accompanying person, and should specify the subject- matter of the proposed oral submissions.

(ii) The request should be made sufficiently in advance of the oral proceedings so that all opposing parties are able properly to prepare themselves in relation to the proposed oral submissions.

(iii) ... ."

The statement that Mr. Jeworrek would "refer to the prior art documents cited by the opponent" is very general.

Therefore, the information provided by the appellant about the subject-matter of Mr. Jeworrek's proposed oral submissions was not sufficient to enable the respondent to prepare itself properly.

For these reasons, the board exercised the discretion referred to in G 04/95 by not permitting oral submissions from Mr. Jeworrek.

Main request

3. Inventive step

3.1 The objective of the patent in suit was "to develop an anticorrosion coating for metal parts, preferably free of hexavalent chromium, that has anticorrosion properties" (see paragraph [0001]).

3.2 The closest prior art

Whereas the respondent considered document (D34) to be the closest prior art, the appellant argued during oral proceedings before the board that document (D14) was the closest state of the art.

The closest state of the art is normally a prior-art document disclosing subject-matter with the same objectives as the claimed invention and having the greatest number of relevant technical features in common.

The objective defined in point 3.1 above corresponds to that of document (D14) which refers to the treatment of zinc surfaces to prevent corrosion (see the title) and to the replacement of chromate as a corrosion inhibitor (see the first paragraph under the heading "1. Introduction" on page 2201). Likewise, the object of document (D34) was "to develop an anti-corrosion coating for metal parts, preferably a coating free of hexavalent chromium, which is endowed with improved anti-corrosion properties" (see page 1, lines 4-7).

3.2.1 The coating composition as defined in the present claims contains

- a particulate metal and

- oxides of Y, Zr, La, Ce, Pr and/or Nd

(see claim 1 under point VI above).

Whereas neither (D14) nor (D34) discloses the use of oxides of Y, Zr, La, Ce, Pr and/or Nd, only document (D34) teaches coating compositions containing particulate metal (see claim 1 of (D34)).

3.2.2 Therefore, document (D34) rather than (D14) qualifies as the closest prior art.

3.2.3 Document (D34) claims the use of MoO3 as a corrosion inhibitor in anticorrosion coating compositions containing particulate metal in aqueous phase (see claim 1).

The composition may be used in the motor-vehicle industry (see page 1, line 12).

The subject-matter of the present independent claims differs from that disclosed in document (D34) only in that (D34) does not disclose the addition of oxides of Y, Zr, La, Ce, Pr and/or Nd.

3.3 The problem to be solved

3.3.1 The French equivalent (D1) of document (D34) is cited in paragraph [0002] of the patent in suit. The patent in suit defines the problem to be solved as "to improve the anti-corrosion properties of compositions containing particulate metal" (see paragraph [0005]).

3.3.2 Neither the patent in suit (or the respective application as filed) nor document (D34) gives any indication that the problem to be solved was a partial or total replacement of toxic molybdenum oxide (MoO3) as a corrosion inhibitor. Therefore, the board is not convinced by the appellant's line of argumentation (see the first paragraph under the heading "Inventive step and sufficiency of disclosure" under point VII above).

Moreover, the person skilled in the art was not likely to pose such a problem, as the data-sheet (D33) reports damage to the respiratory tract and lung cancer only upon inhalation of MoO3. The aquatic toxicity is rather low. As MoO3 as a constituent of an anticorrosive coating is not likely to be inhaled but rather may be washed out by water, the aquatic toxicity seems to be more relevant. Finally, even if the person skilled in the art considered MoO3 to be rather toxic, he would replace it by another corrosion inhibitor only if the latter was less toxic at the concentration required to achieve the same corrosion-inhibiting effect. There is no evidence that the salts and oxides mentioned in the present claims could serve this purpose (see point 3.3.2 of the board's communication of

3 November 2014).

As a consequence, the improvement of the anti-corrosion properties of compositions containing particulate metal as mentioned in point 3.3.1 above constitutes the problem to be solved.

3.4 The problem solved

The appellant argued that Table 11 of the patent showed that the claimed effect was not achieved for the oxides of cerium, neodymium and zirconium. In making this argument, the appellant did not take into account the remaining comparative tests disclosed in the patent in suit. The experiments listed in Table 10 show that the oxides of each of the elements listed in claim 1 of the main request increase the polarisation resistance of the coated substrates with respect to the respective comparative composition 15 or 16, and thus inhibit corrosion. For this reason, the board is satisfied that the problem mentioned above is solved over the whole breadth of the claims (see point 3.3.1 of the board's communication of 3 November 2014).

3.5 The solution of the problem

As a solution to this problem the present claims require the use of at least one oxide of yttrium, zirconium, lanthanum, cerium, praseodymium and/or neodymium in the coating composition.

3.5.1 Document (D34) as such does not disclose or suggest the addition of any compound of any of the above elements. Consequently, this document alone cannot render the subject-matter of the present claims obvious.

Hence, it has to be assessed whether the teaching of any other document(s) of the prior art would have indicated to the person skilled in the art that the addition of oxides of Y, Zr, La, Ce, Pr and/or Nd to the coating compositions disclosed in document (D34) would solve the problem defined above.

3.5.2 In this respect, the appellant relied on document (D14).

This document deals with the treatment of a zinc surface with cerium(III)nitrate (Ce(NO3)3) in order to prevent corrosion by NaCl (see the title). The aim was to find "acceptable and effective corrosion inhibitors as alternatives of chromates ... for protection of zinc and galvanized steel from corrosion". It is also reported that corrosion of galvanised steel by sodium chloride is suppressed by CeCl3 (see page 2202, lines 1-8).

The corrosion inhibiting effect of Ce(NO3)3 is explained by the fact that a protective layer of Ce(OH)3 is formed on the zinc surface because the solubility product of Ce(OH)3 (1.6 x 10**(-20)) is much lower than that of Zn(OH)2. Said hydroxide Ce(OH)3 loses water to form the corresponding oxide Ce2O3. The intermediate steps of the formation of the layer of Ce2O3 are illustrated in equations (8) to (11) on pages 2205-2206.

The appellant argued that the person skilled in the art was inclined to use a cerium oxide directly instead of waiting for the oxide layer to be formed by reaction of the cerium salt. This argument implies that the person skilled in the art would consider it obvious that the use of a cerium oxide instead of Ce(NO3)3 would result in an equivalent protective layer on the zinc surface within a comparable time frame.

However, as the appellant admitted, the corresponding cerium oxide Ce2O3 is only moderately soluble in water. This is in line with the low solubility product of the hydrate Ce(OH)3 of 1.6 x 10**(-20)mentioned above. The person skilled in the art would have expected that the low solubility of the cerium oxide would limit the diffusion of cerium ions to the zinc surface and thus retard or even inhibit the formation of the protective layer of Ce(OH)3 and/or Ce2O3. For these reasons, he would not have expected that the addition of a cerium oxide to the coating compositions disclosed in document (D34) would increase the corrosion resistance of metals coated therewith. Accordingly, the use of respective salts as corrosion inhibitors is also recommended in documents

- (D11) (see the "rare earth metal salts" mentioned in the sentence bridging the columns of the abstract on the front page);

- (D15) (see the nitrates of Ce, La and Pr mentioned in the penultimate full paragraph on page 276);

- (D16) (see the title); and

- (D22) (see the title).

3.5.3 Therefore, the subject-matter of

- claims 1 to 10 which relate to the use of the oxides of Y, Zr, La, Ce, Pr or Nd in coating compositions; and

- claims 11 to 32 which relate to the respective coating compositions

involves an inventive step.

3.5.4 Claims 33 to 39 relate to the corresponding coating and coated metal substrates (see the wording of independent claims 33 and 36 cited under point VI above). The appellant was of the opinion that these coatings and substrates could not be distinguished from those where a salt instead of an oxide of Y, Zr, La, Ce, Pr and/or Nd is used (see the penultimate paragraph under point VII above). This argument is based on the conclusion drawn in document (D14) that the cerium salt is converted to a cerium oxide layer on the zinc surface.

This argument suggests that the oxides of Y, Zr, La, Ce, Pr and/or Nd are completely converted into an oxide layer on the metal surface. It does not take into account the fact that such a conversion takes place only to the extent that ions of these metals diffuse to the metal surface.

The diffusion of these ions to the metal surface is limited not only by the limited solubility of the oxides discussed above, but also by the fact that claim 33 requires

- that the coating is baked and

- that it contains a binder (note that claim 33 refers to the compositions "according to any of claims claims 11 to 32", namely to compositions containing a binder).

Baking will evaporate any solvent and thus render the coating solid. Diffusion within a solid is much slower than in a liquid phase. The binder dilutes the coating and thus forms a further obstacle to diffusion.

Due to this restricted diffusion, the board proceeds from the fact that the coatings and coated substrates according to claims 33 to 39 still contain distinct particles of oxides of Y, Zr, La, Ce, Pr and/or Nd and thus may be distinguished clearly from respective coatings into which these elements were incorporated in the form of their salts. This means that the coatings of claims 33-35 and the respective coated substrates of claims 36 to 39 cannot be produced by any combination of the teachings of documents (34) and (14) but require the non-obvious addition of Y, Zr, La, Ce, Pr and/or Nd in the form of oxides (see point 3.5.3 above).

Hence, the subject-matter of claims 33 to 39 also involves an inventive step.

3.5.5 It is apparent from point 3.5.2 above that the conclusions drawn in points 3.5.3 and 3.5.4 would be no different if document (D14) was considered to represent the closest prior art.

4. Article 100(b) EPC

The appellant based its objection on the fact that Table 11 of the patent shows no improvements in corrosion inhibition upon the addition of the oxides of cerium, neodymium and zirconium. It concluded that the invention was not sufficiently disclosed (Article 100(b) EPC). For the reasons set out under point 3.4 above, the board does not share this view.

Hence, no grounds under Article 100(b) EPC prejudice the maintenance of the patent in suit.

5. Clarity of the claims

The appellant argued that the expression "aqueous phase" in claim 1 was vague and rendered the claims unclear.

A lack of clarity is not a ground for opposition under Article 100 EPC. Accordingly, it was decided in G 03/14 of 24 March 2015 that

"the claims of the patent may be examined for compliance with the requirements of Article 84 EPC only when, and then only to the extent that the amendment introduces non-compliance with Article 84 EPC"

(see the order).

The expression "aqueous phase" already formed part of claim 1 as granted. The appellant had not claimed, and nor does the board have any reason to believe, that any amendment after grant introduced the alleged lack of clarity.

Hence, the alleged lack of clarity also does not prejudice the maintenance of the patent.

6. The appellant has not raised any further objections against the claims of the main request, and nor is the board aware of any deficiency which might prejudice the maintenance of the patent based on that request.

Consequently, there is no need to deal with the auxiliary requests.