(A Slim Monograph by Barrie Gillings)
This booklet is published by the Derby Phantom Register of the Rolls-Royce Owners’ Club of Australia (NSW) Inc., Box 2754 G.P.O. Sydney, NSW 2001 Australia. ABN: 42327 667 396 Whilst all care is taken, the information and advice in this booklet is the record of the experiences or views of its authors and are not necessarily endorsed by the RollsRoyce Owners’ Club of Australia (New South Wales Branch) Inc, the Club’s officials or its individual members. Advice given in this booklet is gratuitous and readers should seek an independent opinion. The Club and the authors cannot be held responsible for any information, advertisement or transaction published in, or begun through this booklet.
HOW THIS BOOKLET CAME TO BE
In recent years, the Registrars of various Registers have arranged for seminars to be held at RROCA Federal Rallies. For the 54th Federal Rally “Ecstasy in Paradise”, seminars were conducted for the Pre-war Small Horsepower Register, the Silver Wraith, Silver Dawn, Mk VI and R Type Register and the Derby Phantom Register. Brian Crump, the Registrar for the Derby Phantom Register, asked me to give a talk on aluminum cylinder head corrosion, a subject of considerable concern to me, as my Phantom II has had this problem. Because of my scientific background, I conducted a series of experiments, and did some research, which I thought might be of interest to fellow owners.
A small but enthusiastic group of Phantom owners attended my presentation, and some were sufficiently interested to ask for a digest of it. Brian Crump urged my wife Margaret and me to prepare a booklet covering the subject, and this record of my research, its related physics and chemistry and what I discovered during my cylinder head restoration is the result.
Some readers may feel that the areas I covered are surplus to their requirements, and may be tempted to skim-read them or by-pass them entirely. I urge them to persevere, because a well-informed owner is much less likely to be bamboozled by an opportunistic R-R or B car salesman, or even worse, a hungry ‘restoration specialist’.
I have written the areas covered in this booklet in a way which I hope allows understanding without the need for exam-passing skills in Physics I or Chemistry I, so there is no quiz at the end. But if, having read it, you understand that radiator water should be as pure as you can afford, that you should not add ethylene or propylene glycol (unless you live where rivers and creeks freeze) and that anything you do add is simply to suppress corrosion and foaming, this booklet will have achieved its aim.
THE BASIC SCIENCE
The Periodic Table lists the chemical elements according to the number of electrons orbiting their atoms. The first is Hydrogen (H1), which consists of a positively charged Proton, with one negatively charged orbiting Electron. (Fig 1, left). The next is Helium (He2) right, with two protons, and two orbiting electrons. Lithium (Li3) is next, with three protons and three electrons, but its third electron starts a new ‘layer’ of electrons. Beryllium (Be4) is next with two outer shell electrons. On the right are Boron, Carbon, Nitrogen, Oxygen, Fluorine and Neon, with 3, 4, 5, 6, 7 and 8 outer shell orbiting electrons. It is the matching Protons (and Neutrons) in the atoms that give them weight, and the outer ‘layer’ of electrons which dictate the element’s chemical behaviour. Element 11, Sodium, starts another new layer of eight electrons, and this layer of eight ends with element 18, Argon (A). The next layer can accommodate 18 electrons, starting with 19, Potassium (K), and ending with 36, Krypton (Kr).
The periodic table arranges the elements in recognizable groups, shown here separated by dark lines with the light metals on the left, the inert gases (which have complete electron layers) on the right, high melting metals in the middle, (further separated into brittle, ductile, noble and low-melting) and non-metals on the right. The ‘complete’ layers, or ‘shells’ of orbiting electrons are maximums of two, then eight, eight, eighteen, eighteen and eighteen The chemical and electrical behaviour of elements depends entirely on the behaviour of the outer layer of orbiting electrons, and their weights the number of Protons and Neutrons in their nucleii. Only the outer electrons take part in chemical reactions.
The atoms of metals are solid at room temperature (except Mercury (Hg)) and arrange themselves, through mutual attraction, in the crystalline patterns of face-centered cubic, body-centered cubic or close-packed hexagonal. Melting destroys these patterns, and when cooling, the atoms re-assemble in their specific crystalline patterns. The individual crystals grow larger as they cool and accumulate more atoms, until eventually they come up against a neighboring crystal and growth ceases. These interfaces, which are three-dimensional, are called grain boundaries.
If an appropriate acid is applied to a polished metal surface, the grain boundaries are preferentially etched, and display the grain structure. This technique reveals much about the nature of the metal or alloy, and helps to explain its behaviour.