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).
Minimizing corrosion in engine cooling systems, discussing causes on Ph.III cars and solutions like anodic oxidation.
| Identifier | ExFiles\Box 150\3\ scan0363 | |
| Date | 21th February 1938 | |
| -4- These facts lead us to think that one of the most effective ways of minimising corrosion is to ensure that no water loss, and hence no replenishment takes place. For preference this should be done by sealing the system with a steam valve so reducing the likelihood of aeration of the cooling water. (2) We think that the large amount of corrosion product in the water systems of the early Ph.III cars which have given so much trouble due to matrix choking, was due primarily to the fact that the steam valves in these cars were not correctly set before the chassis left the works. This necessarily resulted in severe water loss (since these cars had 6 port cylinder heads and a good sealing steam valve is essential to prevent water loss with this type of head) with consequent replenishment, resulting in continual corrosion taking place. Further, the steam valve is placed in such a position that if leaking, it will tend to let water and vapour escape while retaining the heavier corrosion deposit which will probably not rise easily to the highest point of the top tank. The iron hot spot box was, of course, a contributory cause of the corrosion. (3) Systems which have both cast iron and aluminium in them appear to be considerably more affected with corrosion by water replenishment and aeration generally, due presumably to electrolytic action between the iron and aluminium. (4) Anodic oxidation of the aluminium parts in contact with the water greatly reduces the corrosion of these parts, in fact, except at spots where the anodic skin is broken it stops it altogether. We have ascertained that Messrs. Daimlers make a practice of anodically oxidising all parts of their water system in contact with the coolant. We have obtained an estimate as to the cost of this treatment if standardised on the Ph.III chassis, i.e. treating cylinder heads, c/case, top water rails, hot spot box, water pump and oil cooler box - this amounts to an initial plant cost of approximately £60 (plus fixing charge), a fixed charge for maintenance of solution of 15/- per week which is largely independent of production and a charge of 3/7d. per chassis for labour and power consumption. | ||