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).
Research committee report comparing anodising and tin-plating of aluminium alloy pistons.
| Identifier | ExFiles\Box 148\1\ scan0038 | |
| Date | 1st January 1939 | |
| File 1258 I.A.E. AUTOMOBILE RESEARCH COMMITTEE Research Department, Great West Road, Brentford, Middx. No. 9200. Class 255, 90, 42. January, 1939. Anodising Versus Tin-Plating of Aluminium Alloy Pistons E.{Mr Elliott - Chief Engineer} Nitzsche and H.{Arthur M. Hanbury - Head Complaints} Klemm, Metallwirtschaft, October 28, 1938, pp. 1143-1147. It is shown by means of numerous micrographs that the anodised layer develops out of the base metal to which it is closely bound, whereas in the tin-plating process the pores and other surface irregularities are not coated, and tin is not precipitated on alloy constituents which are insoluble in the bath (e.g., Si). Comparative cold starting tests were carried out on a B.M.W. six-cylinder engine of 2 litres capacity, fitted with three tin-plated and three anodised pistons of equal dimensions. The engine was cooled to between -12 and -15°C. and immediately after starting speeded up to 4,000 r.p.m. without load. This procedure was repeated five times with a low viscosity winter oil (Essolube 20). In the subsequent tests a viscous oil (Shell XXX) was used, and seven cold starts were carried out in a similar way without engine failure. In order further to increase the severity of the test the temperature of the cooling fluid was maintained between -7 and -9°C., and the oil temperature between -10 and -12°C. Immediately after starting, full load was applied at 4,000 r.p.m. In the second start of this kind seizure occurred after 30 seconds' operation. It was found that one tin-plated piston was scuffed on the non-thrust side and, also, the cylinder showed traces of scuffing. The coating on the tin-plated pistons was partly removed, whereas the anodised pistons did not show any signs of damage. The authors conclude that, in view of the lack of sufficient practical experience on tin-plated pistons, further investigation will be necessary before a final judgement can be given on the merits of this method of surface treatment. L.R. | ||