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England and Wales Court of Appeal (Civil Division) Decisions
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Cite as:  EWCA Civ 177
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COURT OF APPEAL (CIVIL DIVISION)
ON APPEAL FROM THE HIGH COURT OF JUSTICE
CHANCERY DIVISION (PATENTS COURT)
The Hon Mr Justice Pumfrey
HC 04 C00060
Strand, London, WC2A 2LL
B e f o r e :
LORD JUSTICE SCOTT BAKER
LORD JUSTICE JACOB
| Saint-Gobain PAM SA
|- and -
|Fusion Provida Limited
Electrosteel Castings Limited
Smith Bernal Wordwave Limited, 190 Fleet Street
London EC4A 2AG
Tel No: 020 7421 4040, Fax No: 020 7831 8838
Official Shorthand Writers to the Court)
Jacobson Llp) for the Respondent/Claimant
Roger Wyand QC and Jonathan Hill (instructed by Messrs Bird & Bird)
for the Appellants/Defendants
Crown Copyright ©
Lord Justice Jacob:
Dates and other basic matters
Common General Knowledge
(a) It was obviously desirable that buried pipe should be resistant to corrosion over very long periods, not least because corrosion was not readily detectable in use and the cost of replacement generally higher than for accessible pipes.
(b) Such piping was typically made of cast iron.
(c) "Black pipe" was and had for many years been in widespread use as a successful form of corrosion resistant iron piping for buried use. It was made from three layers: the main, structural layer of ductile cast iron, a layer of Zn and a layer of bitumen.
(d) Absent the protective coating, the iron would corrode very readily, particularly in hostile (e.g. acid or saline) soil conditions. You hardly need to be a "skilled man" to know that!
(e) The protective coating of Zn was not provided by hot dipping or true galvanisation (i.e. electrolytic deposit). It was sprayed on and so was slightly porous. The outermost layer, sometimes called the "pore-sealing" layer was also slightly porous.
(f) For non-buried (above-ground or marine) iron or steel (which itself is mainly iron) a coating of Zn can provide protection by two distinct mechanisms. Firstly, it can simply act as a protective coating preventing water and oxygen from reaching the iron like a coating of paint or bitumen. Second, however, there is the possibility, if the Zn coating gets wet, of electrolytic action. This is also called "galvanic" or "sacrificial" protection. When iron and Zn are in contact and the combination is in water containing an "electrolyte" (free ions, as for instance in acid conditions) the Zn will preferentially corrode. It is not necessary to explain more here though every A-level (and probably GCSE) chemistry student will know this.
(g) In the case of black pipe a further anti-corrosion effect comes into play. Because it is slightly porous, the surrounding (corrosive) medium penetrates within the Zn. A rigid impermeable layer of Zn corrosion products forms. In due course all the Zn is consumed. So galvanic protection stops. But by then there is a layer of Zn corrosion products. This is itself so tough and coherent that it forms a physical barrier to corrosive products. This barrier lasts for many years. So one gets protection extending well beyond "the life" of the Zn.
(h) During the early period of this process another important and remarkable phenomenon occurs. It is hardly surprising that when pipe is being buried it is liable to take a few knocks and get scratched. So some of the underlying iron will get exposed. This is an obvious and serious danger exposed iron should, in principle, corrode much faster than protected iron. But it turns out that the Zn corrosion products actually migrate to the exposed iron to the site of the damage. The protective skin of Zn corrosion products builds up on this too. This is obviously very important indeed.
(i) There were particular problems with very acidic soils. In these the Zn corrosion product skin would not form. There was a need for a better form of corrosion protection for buried pipe one that could cater for more stringent conditions than could the existing Zn based black pipe.
(j) Mixtures of Zn and Al (as an alloy) were also well-known for general use in corrosion protection. They had been used for years for above-ground and marine uses. But not for buried pipes. It was not known whether such an alloy would also form a protective corrosion skin or would do so as well as Zn alone. The purpose of the Al in the known uses was to slow down the erosion of Zn by galvanic effects.
The Patent in Suit
"The purpose of the invention is to provide a coating technique for a buried iron-based pipe member which is suitable regardless of the purpose of the piping, particularly for water supply and drainage, in most types of soil, at an acceptable cost."
"1. An iron-based, in particular cast iron, pipe member for buried piping, which is provided with an external coating comprising:
- a first porous layer of zinc/aluminium alloy containing 5 to 60% of aluminium; and on this first layer,
-a second porous layer, called the pore-sealing layer, based on organic or inorganic binder in aqueous, solvent or powder phase, between 100 and 140΅m thick."
"Through the action of corrosive agents in the soil this layer is converted into a protective layer of stable corrosion products in the environment in which it develops. The alloy layer is also called a "sacrificial" layer with respect to the cast iron, in the sense that it can be consumed progressively by oxidation as a result of the electrochemical cell formed by the cast iron, the alloy and the soil, to protect the cast iron underneath or bared at [sic] defects in the layer of zinc-aluminium alloy, through the formation of the said protective layer.
It has been found that the two-phase structure of the Zn/Al alloy favours the trapping of Zn corrosion products."
"The finishing layer, called the pore-sealing layer, is then deposited by spraying. This pore sealant both slows down corrosion of the zinc and consolidates the layer of zinc corrosion products, in order to maintain their protective effect. The thickness of the pore sealant should be sufficient to ensure that this retention takes place, but sufficiently thin for the pore sealant to remain porous, failing which the active species could no longer migrate to the first layer of the coating in order that this first layer plays its part as explained above. Furthermore, too great a thickness of the pore sealant would trap water beneath it and form blisters."
"From eleven years' field tests the following conclusions can be drawn:
- Aluminised steel is in general not more corrosion resistant than galvanised steel in soil.
- If a long technical service life is desired, the following is recommended:
- For less aggressive soil (e.g. sand), thick aluminium or zinc coatings with a coating thickness of at least 200 ΅m.
- For very aggressive soil (e.g. clay), very corrosion resistant material is required. A thick coating (200 ΅m) with 50% aluminium 50% zinc seems promising."
The approach to obviousness
(1) Identify the inventive concept of the claim;
(2) Identify the common general knowledge;
(3) Identify the difference(s) between the prior art and the alleged invention;
(4) Decide whether those differences would have been obvious steps.
"This case has given me a great deal of difficulty. My opinion has changed more than once. The various factors to which I have referred seem to me to be rather evenly balanced, but I am influenced in the end by the historical considerations to which I have referred. This can almost be described as a case in which the alleged invention ought to have been obvious. Nonetheless, I conclude that claim 1 of the patent is valid."
"I conclude that there are strong technical reasons for supposing that this is, in fact, a case of a simple substitution of one known protective layer for another, suggested by Johnsson."
The approach on appeal
"The need for appellate caution in reversing the judge's evaluation of the facts is based upon much more solid grounds than professional courtesy. It is because specific findings of fact, even by the most meticulous judge, are inherently an incomplete statement of the impression which was made upon him by the primary evidence. His expressed findings are always surrounded by a penumbra of imprecision as to emphasis, relative weight, minor qualification and nuance (as Renan said, la vιritι est dans une nuance), of which time and language do not permit exact expression, but which may play an important part in the judge's overall evaluation. It would in my view be wrong to treat Benmax as authorising or requiring an appellate court to undertake a de novo evaluation of the facts in all cases in which no question of the credibility of witnesses is involved. Where the application of a legal standard such negligence or obviousness involves no question of principle but is simply a matter of degree, an appellate court should be very cautious in differing from the judge's evaluation."
The arguments on appeal
"If there is any inventive step involved in the appellants' claim, it is in the idea of using a known, but recently developed, flocculating agent in a known filtration process"
"The learned judge preferred the expression 'see without difficulty that these newly-introduced polymers would be of advantage in his filtration step.' I think that 'would be' puts it too high if it postulates prior certainty of success before actually testing the polymers in the filtration process; it is enough that the person versed in the art would assess the likelihood of success as sufficient to warrant actual trial"
"Q. And then you say: "However, it should be noted that only one exposure test was carried out for sprayed zinc-aluminium (in clay with sample exposed above the groundwater table) and the samples were only examined at the end of the 11 year test period. Hence any conclusions from the performance of zinc-aluminium spray coating may be regarded as being at best speculative." Will you accept that the conclusion that is stated there is a clear suggestion that the 50-50 alloy coating is something that is worthy of further investigation?
A. Based on a single test sample, then I agree, yes, it would be worthy of investigating in that particular type of extreme, the aggressive soils."
"Q. Can I suggest you are going to test things that people suggest have some promise and those are the ones you are going to concentrate on provided there is not some reason why you think it is definitely not going to work, you are going to test the ones people describe as having some promise?
A. You will test things described as having some promise but the situation, again, is that just because something is considered interesting in a research viewpoint does not mean you have any high expectations of it working. But, yes, if you had zero expectation of it working, you would not test it.
Q. Well worth trying?
A. Difficult question to answer. Depends what the particular criteria are for your test programme, what your other alternatives are, how they weigh in compared to the promise as devised by the salesman who is trying to get you to use that particular coating or that particular system. If you were just looking at these in isolation, then maybe. If you are looking at them as part of an overall test matrix. Without knowing what the overall test matrix is, I could not say whether or not they would be top of the list, middle of the list, bottom of the list."
"Q. Therefore, a logical way of proceeding is to try some zinc aluminium alloys to see whether the aluminium removes the advantage of zinc or whether it cooperates with it.
A. What you get from Johnsson tells you that the aluminium zinc works well in that particular soil condition, which is particularly acidic; which would indicate, yes, if you were aiming purely to develop a coating for acidic soils, that would be a way to proceed. In terms of moving into a more general soil condition, away from either the salinity or the pH, then the other concerns, as I mentioned above in terms of the performance of the aluminium in any protective film and possibly, as you move away from saline conditions, whether or not you are getting any degree, or the extent of the degree of galvanic protection, is still the question. In answer, testing, I could consider it, yes it would be part of the test matrix. As I say, whether it would be your great white hope or otherwise, I could not say.
A. . As has been said numerous times over the last few days, the key issue that was identified in the '92 Compendium is the performance of zinc in soils in the ways that it is not just providing protection whilst the zinc is intact, but also longer after it has disappeared. That is the surprising nature, not just in the general coating which is formed in the interstices within the coating itself, but the fact that the gap protection layer develops initially by the galvanic action, but then that particular coating remains intact and provides protection long after any drivers have disappeared.
Q. That was surprising, but it was known by 1992 that that is how zinc worked?
A. And that is the key nature of why zinc works. So before you would even contemplate anything else, you would want to be assured that anything you do maintains that protection. There is no point in having a better coating in the sense that it lasts intact for a longer period and then all protection is then instantly evaporated.
What you are looking for is a situation which is described mainly in the steel and concrete industry; as the time to imitation of corrosion, then development of the corrosion thereafter, until you reach the failure state. What the black coating does, you have the zinc remains for a particular period where, essentially, no corrosion of the substrate occurs, then the zinc salts remain behind, which then provide protection. I am not necessarily saying that is zero corrosion occurring. It is providing protection thereafter, so it is corroding at a slowish rate.
If you had a situation where you were putting and you modified that metallic coating so it lasted longer, this is fine for your period to initiation; but if then there was no ongoing protection, your end life, your total engineering life of the product, would be nowhere near as strong. That, as far as I understand it, is the key feature, which is what is being it is the long-term, the 80 years-plus, life which is what has been aimed at."
Lord Justice Scott Baker:
Lord Justice Peter Gibson:
ORDER: Appeal dismissed; the appellant to pay the respondent's costs of the appeal (including the respondent's notice) to be the subject of detailed assessment if not agreed; permission to appeal to the House of Lords refused.