PUT THIS IN YOUR PIPE - BUT DON'T CORRODE IT

Here's a decision from the Court of Appeal on Friday, in Saint-Gobain PAM SA v Fusion Provida Ltd and another [2005] EWCA Civ 177.

St Gobain, a large company that made underground pipes for sewage and water supply, owned a patent for a method of coating buried iron-based pipes which made them resistant to corrosion. The invention was described in claim 1 of the patent as comprising a first porous layer of zinc/aluminium alloy, in place of zinc, and a second porous layer, the pore-sealing layer, based on organic or inorganic binder in aqueous, solvent or powder phase. St Gobain sued FP, a small competitor, for infringement proceedings in which it was accepted that, if the patent was valid, FP infringed it.

As to validity FP contended that the invention was obvious, having regard to disclosure in a paper published by the Swedish Corrosion Institute just before the priority date. That paper, entitled ‘Corrosion resistance coatings of aluminium, zinc and their alloys’, concerned testing of differently coated steel plates. No pipes were tested, nor was there testing of any samples which had a porous second layer – what the patent called a ‘pore sealing layer’. The paper did not mention any observation of zinc corrosion products and there was no attempt to observe what happened to small areas of exposed steel, which was an important aspect of buried pipe protection. In approaching the question of obviousness, Mr Justice Pumfrey found that the inventive concept was black pipe, but made with aluminium/zinc alloy instead of zinc. He found that the case was evenly balanced, as there were strong technical reasons for supposing that the case was, in fact, one of simple substitution of one known protective layer for another, as suggested in the Swedish paper. He was ultimately swayed, however, by historical considerations and held the step to be non-obvious and the patent therefore valid.

FP appealed, arguing that the trial judge had erred and that the historical considerations which tipped the balance were irrelevant. They submitted that, since the Swedish paper had been published only just before the priority date, there was simply no room for historical considerations and that the judge’s view, apart from historical consideration, that the case was one of substituting one protective layer for another, as suggested by the paper, should prevail.

St Gobain: Court of Appeal affirms the validity of its patent

The Court of Appeal, Civil Division (for whom Lord Justice Jacob as usual gave the judgment) dismissed FP's appeal. The reason why historical reasons were important when the Swedish paper came to be considered was simple: the use of zinc/aluminium in place of zinc as an anti-corrosion coating for above ground and marine anti-corrosion coatings had been known for some years. One might well think, in the absence of the history, that it was self-evident that simple substitution would work or might very well work for buried pipes too. However, no-one had actually taken that step and there was nothing in the Swedish paper to galvanise the skilled man into action. Nothing in the paper had made the idea of using zinc/aluminium for pipes obvious.

The IPKat was intrigued by this historical approach, which hadn't really occurred to him before.

Rusty pipes here and here