Non-metallic materials

Besides large-diameter pipes, ultrasonic testing is used for checking the welded joints of drill bits, components of wind-driven electric plants, welded joints of light alloys and non-metallic materials, for an integrated inspection of various objects. A range of training aids developed at the Institute allows the operators to be trained effectively. 

SUGGESTED METHOD FOR THE RATIONAL ANALYSIS OF THE NON-METALLIC MATERIALS... 

D. Raybould and T.Z. Blazynski, Non-metallic Materials under Shock Loading, in Materials at High Strain Rates (edited by T.Z. Blazynski), Elsevier/Applied Science, London, 1987, 71 pp. 

The insulation around the central electrode is an example of a non-metallic material - in this case, alumina, a ceramic. This is chosen because of its electrical insulating properties and because it also has good thermal fatigue resistance and resistance to corrosion and oxidation (it is an oxide already). 

Newnham, R.E. (1975) Structure-Property Relations (in a monograph series on Crystal Chemistry of Non-Metallic Materials) (Springer, Berlin). 

AMD 1 Eire hazard testing. Part 2 Test methods. Needle-flame test (AMD 9176J dated 15 November 1996. Previously known as BS 6458 Section 2.2 1993 Eire hazard testing. Terminology concerning fire tests. Superseded BS 6458 Part 1 1990 Elammability of solid non-metallic materials when exposed to flame sources - List of test methods. Superseded BS 6334 1983... 

Attention is drawn to Regulation 4(2) of the Gas Safety (Installation and Use) Regulations, which prohibits the use of non-metallic materials for gas pipework other than for small portable appliances such as Bunsen burners and lighting torches. 

Corrosion is generally taken to be the waste of a metal by the action of corrosive agents. However, a wider definition is the degradation of a material through contact with its environment. Thus, corrosion can include non-metallic materials such as concrete and plastics and mechanisms such as cracking in addition to wastage (i.e. loss of material). This chapter is primarily concerned with metallic corrosion, through a variety of mechanisms. 

Carbon dioxide produces a solution of carbonic acid (as in boiler condensate, see Section 53.3.2). Carbon steel is often employed but corrosion rates of up to 1 mm/yr can be encountered. Coatings and non-metallic materials may be employed up to their temperature limits (Section 53.5.6). Basic austenitic stainless steels (type 534) are suitable up to their scaling temperatures. 

The interaction of a metal or alloy (or a non-metallic material) with its environment is clearly of vital importance in the performance of materials of construction, and the fact that the present work is largely confined to a detailed consideration of such interactions could create the impression that this was the sole factor of importance in materials selection. This, of course, is not the case although it is probably true to say that this factor is the one that is the most neglected by the design engineer. 

In the case of non-metallic materials, the term corrosion invariably refers to their-deterioration from chemical causes, but a similar concept is not necessarily applicable to metals. Many authorities consider that the term metallic corrosion embraces all interactions of a metal or alloy (solid or liquid) with its environment, irrespective of whether this is deliberate and beneficial or adventitious and deleterious. Thus this definition of corrosion, which for convenience will be referred to as the transformation definition. 

On the other hand, corrosion has been defined as the undesirable deterioration of a metal or alloy, i.e. an interaction of the metal with its environment that adversely affects those properties of the metal that are to be preserved. This definition —which will be referred to as the deterioration definition —is also applicable to non-metallic materials such as glass, concrete, etc. and embodies the concept that corrosion is always deleterious. However, the restriction of the definition to undesirable chemical reactions of a metal results in anomalies which will become apparent from a consideration of the following examples. 

Protective measures against bimetallic corrosion should ideally start before the particular installation or equipment is built . Reference should be made to tables showing compatibility of metals, alloys and non-metallic materials (5 Table 1.25) and to the literature. However, it must be emphasised that the environment obviously plays a most important role in bimetallic corrosion, and that there are a number of situations in which apparently incompatible materials in contact can be used without adverse effects. 

It is not worth while, therefore, to give a digest of experimentally determined corrosion rates , but Table 2.21 indicates some sources of such data and their nature. (Some references to data on compatibility of fused salts with non-metallic materials have been included for the sake of completeness.) It should be remembered, that in the case of alloys, failure usually arises from selective attack which causes porosity of the container, even though the wall may appear on casual inspection to be quite sound... 

Much of the early work on fretting was confined to mild steel or carbon steel. Although many of the same principles apply to the fretting of other metals such as gold , titanium and the superalloystheir reaction to the environment may be a more significant factor. In addition, non-metallic materials such as polymers composites and ceramics are becoming widely applied and the principles of contact here are very dififerent from the metallic case. 

Non-Metallic Materials Numerous engineering thermoplastics have been commercialised including materials such as polyetherether ketone (PEEK) and polyether sulphate (PES) with much improved thermal/chemical resistance. The usage of FRP equipment has increased, and fluoropolymer lining technology/applications have come of age. Of particular interest is the development of stoved, fluoropolymer coating systems for process industry equipment. 

Non-metallic materials can provide cost-effective and secure solutions... 

Cans with replaceable closures for such products as dry foodstuffs, pharmaceuticals, tobacco, solvents, liquid fuels and paint. These usually contain an appreciable amount of oxygen. Tinplate closures for bottles and jars made of non-metallic materials may also be considered in this category. 

Chemical deposits of copper are applied to provide conducting surfaces on non-metallic materials. 

Since corrosion involves a reaction of a metal with its environment, control may be effected through either or both of the two reactants. Thus control could be based entirely on the selection of a particular metal or alloy in preference to all others or the rejection of metals in favour of a non-metallic material, e.g. by a glass-reinforced polymer (g.r.p.). At the other extreme control may be effected by using a less corrosion-resistant material and... 

Select metal or alloy (or non-metallic material) for the particular environmental conditions prevailing (composition, temperature, velocity, etc.) taking into account mechanical and physical properties, availability, method of fabrication and overall cost of structure. Decide whether or not an expensive corrosion-resistant alloy is more economical than a cheaper metal that requires protection and periodic maintenance. 

Non-metallic Materials Carbides, carbon, ceramic fiber, ceramic, cermet, composite, cork, elastomer, felt, fiber, glass, glycerin, non-metallic bearing material, rubber (natural), rubber (synthetic), silicone, wood, leather. 

Trautschold, R. (1940). Non-corrosive, non-metallic, materials. Rayon Textile Monthly, 21, 373-4. 

More data on polymers and other fibre-reinforced polymers can be found in the proceedings of various ICMC (International Cryogenic Materials Conference) meetings devoted to non-metallic materials and composites at low temperatures [113-117] and some special issues of the journal Cryogenics [118-120]. 

Unless otherwise specified, the need for hard-facing and the specific hard-facing material for each application is determined by the vendor and described in the proposal. Alternatives to hard -facing may include opening running clearances f.7.4) or the use of non-galling materials, such as Nitronic 60, Waukesha 88, or non-metallic materials, depending on the corrosiveness of the pumped liquid. 

Atomic structures of surfaces of non-metallic materials (a) Silicon surfaces... 

---