From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Methods for protecting Nitralloy steel, specifically the tinning process versus copper plating.
| Identifier | ExFiles\Box 154a\1\ scan0157 | |
| Date | 1st May 1929 | |
| RHC.{R. H. Coverley - Production Engineer} HI. Hs.{Lord Ernest Hives - Chair} G.BY/BM. X4469 BY9/G.1.5.29. NITRALLOY STEEL. ---------- With reference to the protection of nitralloy steel, I understand from Mr. Hall that an attempt is being made to protect the steel where it is required to be kept soft by copper plating. My object in writing is to point out that this method has been tried on numerous occasions by the originators of the nitralloy steel, and has proved to be inadequate; in the same way electro tinning is quite inadequate. It is of the utmost importance that we should concentrate upon our methods of fluxing and tinning, as this is really where the difficulty lies. It is not sufficient to merely coat a piece of material with tin as a protection, as if the base is not chemically cleaned the necessary tin iron alloy which gives the protection is not formed, and therefore the part when treated will harden on the surface which apparently has been protected. The protection against the penetration of nitrogen is not merely the presence of a tin coating, as obviously this must melt off at a temperature far below that required for the ammonium treatment. The protection is provided by the formation of a tin iron alloy which cannot be melted off the surface, and which is therefore perfectly stable even up to 600°C, and forms an impenetrable coat through which the nitrogen cannot pass. I suggest that we should take some sample pieces of plain turned bars, and that Mr. Hall should give his attention to the question of fluxing and tinning these parts until we have definitely been able to produce a sufficiently clean surface on the iron to enable the tin iron alloy to be formed; without this coating the attempt to produce protection by tinning is valueless. One further point, I would suggest that we should produce some parts up to the stage at which they are to be tinned and protected, and that these should be sent to Messrs. Firth Derihons for them to tin the parts. These again only need be plain turned bars, and we could then make a comparison as to whether our methods are as successful as those of Firth Derihons or Nitralloy Ltd. who are associated | ||