Corrosion

“ When a sufficient concentration of chloride ions reaches the rebar, corrosion begins. The corrosion stage begins at the onset of corrosion and lasts until failure of the of the steel reinforcement, which is typically only a few years hence. Since the initiation stage may last for hundreds of years, the duration of the corrosion stage is insignificant to the total lifetime of the reinforcement. ”

“ The formation of carbonate takes place with considerable rapidity. In twelve ounces of distilled water, contained in a shallow glass basin loosely covered to exclude the dust, twelve brightly polished lead rods weighing 340 grains, will lose two grains and a half in eight days; and the lead will then show evident marks of corrosion. The process of corrosion goes on so long as atmospheric air is allowed to play freely on the surface of the water. In twenty months I have obtained 120 grains from an ounce of lead rods kept in 24 ounces of distilled water. ”

“ Metallic substances, such as iron, copper, bronze, brass, tin, and lead, whether they exist in stones, or are used for support or connection in buildings, are liable to be corroded by water holding in solution the principles of the atmosphere; and the rust and corrosion, which are made, poetically, qualities of time, depend upon the oxidating powers of water, which by supplying oxygen in a dissolved or condensed state enables the metals to form new combinations. ”

“ The greatest danger to be guarded against is corrosion, as all injecting fluids which are now in use contain more or less of either acids or metallic salts, all of which will attack and corrode, to a lesser or greater extent, the metals and other substances with which they come in direct contact. ”

“ The second part of the process is the corrosion, or, as it is technically called, biting in. This is effected by pouring upon the design a quantity of diluted nitric acid, after having surrounded the edges of the plate with a wall of soft wax, to prevent the escape of the fluid. A chemical action immediately takes place in all the lines or points where the copper has been denuded by the needle. After the first biting has been continued long enough, in the judgment of the operator, the acid is poured off, and the plate examined. ”

“ Corrosion—Where there is a corrosive action because of the presence of acid in the water or of oil containing fatty acids which will decompose and cause pitting wherever the sludge can find a resting place, it may be overcome by the neutralization of the water by carbonate of soda. ”

“ So long as the zinc surface remains intact, the underlying metal is protected from corrosive action, but a mechanical or other injury to the zinc coating that exposes the metal beneath, in the presence of moisture causes a very rapid corrosion to be started, the galvanic action being changed from the zinc positive to zinc negative, and the iron, as the positive element in the circuit, is corroded instead of the zinc. ”

“ Iron and steel are of no use now; the corrosive power of our atmosphere is so great, that the heaviest and strongest structure if made of these metals would soon be eaten away. The great war ships of the ancients and their great merchant fleets soon became useless by corrosion. ”

“ It is sometimes asserted that corrosion cannot be the cause of an explosion, because the corroded place would simply give way and let off the steam harmlessly, or at least the boiler would not be displaced from its seating. When the corrosion is only local, and surrounded by sound plates of sufficient strength to arrest the extension of the fracture, this may be the case, as in an explosion at Sheffield in 1865, shown in Fig. ”

“ By placing small, brightly polished steel plates into a mush of paint pigment and water, a determination may be made of the pigment’s effect upon the metal. Some pigments, under such conditions, cause rapid corrosion of the steel plates. Such pigments are stimulators of corrosion, on account of acid impurities which they contain, or because of their effect in stimulating galvanic currents. Many carbonaceous pigments are of this type. Other pigments have the effect of keeping bright the steel plates and preventing rust. ”

“ There are other evils sometimes inherent in hard waters above the mere production of a crust. Some waters contain a great deal of soluble magnesia salts, together with common salt. When this is the case there is a great probability of corrosion, for the former is attacked by steam at high pressure in such a way that muriatic acid fumes are produced, which seriously corrode the boiler, and what is far worse, passes with the steam into the engine, and sets up corrosion in the cylinders and other delicate fittings with which the steam comes in contact. ”

“ In the manufacture of white lead processes which create dust are specially dangerous, namely, emptying the corrosion chambers, drying and grinding, transport of the material in the form of powder, and packing. The following measures are called for: emptying the chambers should only be done by men wearing respirators or equipped with breathing helmets after preliminary damping of the corrosions by means of a spray. Use of a vacuum cleaning apparatus suggests itself. Drying should be done as far as possible in stoves charged mechanically, the temperature in which can be watched from the outside ”

“ The application of felt to the outside of a boiler, has in several cases been found to accelerate sensibly its internal corrosion; boilers in which there is a large accumulation of scale appear to be more corroded than where there is no such deposit; and where the funnel passes through the steam chest the iron of the steam chest is invariably much more corroded than where the funnel does not pass through it. ”

“ In parts of the vertical boiler there is very little circulation and the corrosion on the inner side is such as to wear the boiler rapidly. In the ash pit, ashes and any dampness that may be about the place also causes rapid corrosion. The upper part of the tubes and tube sheet are frequently injured; for instance, if the tubes pass all the way through to the upper tube sheet, providing there is no cone top, when the fire is first made under the boiler, combustion at times does not take place until the gases pass nearly through the tubes. ”

“ If deeply corroded nothing can well be done to it; the lumpy crust shows more of the original form than the metal would show if bared. When the corrosion is but slight it may be removed, either by solution in strong ammonia or cyanide of potassium, or by reduction. To bring the chloride into the state of porous metal, it is only needful to place it with zinc or iron in a solution of salt or weak vinegar or lemon juice, and in a few hours the whole of the chlorine has gone over to the fresh metal. ”

“ Supercritical water oxidation equipment, and specially designed waste supply and material handling systems, with reactor volumes of 0.05 m3 (50 litres) or greater, in which all surfaces that come into direct contact with the toxic chemicals are made from corrosion resistant materials. b.4. Direct chemical oxidation equipment, and specially designed waste supply and material handling systems, with reactor volumes of 0.100 m3 (100 litres) or greater, in which all surfaces that come into direct contact with the toxic chemicals are made from corrosion resistant materials. ”

“ Internal corrosion sometimes takes place from bad feed water, and its effects are different in extent in the different parts of the same boiler. It very seldom thins the plate over a large surface regularly, but attacks the iron in spots, pitting it in a number of holes. These are sometimes large, as if gradually increasing from a centre of action; and sometimes small, but so close together as to leave very little more space whole than that which is attacked. A very curious example of the latter was exhibited to the meeting, and shown in Fig. 56 and Fig. ”

“ Corrosion sometimes occurs at the joints of lead pipes, contiguous to the line of solder, and is attributed to galvanic action created by the contact of the zinc and lead, but as these openings are apt to leak they are more liable to discovery. ”

“ A complete removal is practically impossible and as a last resort to obviate corrosion in certain designs, the bottom of the water legs in some cases have been made of copper. A thick layer of mud and scale is also liable to accumulate on the crown sheet of such boilers and may cause the sheet to crack and lead to an explosion. ”

“ The strain caused by the varying temperature of the internal tubes in Cornish or Lancashire boilers, and the difficulty of staying their flat ends so as to make them sufficiently secure without being too rigid to allow for the expansion of the tubes, render them liable to corrosion or "furrowing" in particular lines of strain, the destructive action of which is very rapid; while the large quantity of brickwork around the outside, necessary to form the external flues, also renders them liable to corrosion in the parts most difficult of access. ”

“ Often, in removing the cylinder head and the plate covering the valves of an engine, we see evidences of corrosion or action on the surfaces, differing entirely from ordinary wear, and the engineer is generally at a loss how to account for it. According to the general impression grease or animal oil is the preservative of the metal, and is the last thing suspected of being the cause of its general disintegration. ”

“ This will give the painted object a seemingly-enameled surface, which is durable and not affected by heat, acids, or the action of the atmosphere. When applied to wood it prevents rotting, and it arrests disintegration when applied to stone. It is well known that the inside of an iron ship is much more severely affected by corrosion than the outside, and this paint has proven itself to be a most efficient protection from inside corrosion. It is light, of fine grain, can be tinted with suitable pigments, spreads easily, and takes hold of the fibre of the iron or steel quickly and tenaciously. ”

“ Corrosion by galvanic action may have produced honey combing or a general attack over the surfaces, which have a dark or dark and sparkling appearance, the latter more particularly when corrosive action has been very active. ”

“ External corrosion is a far more frequent cause of explosion in stationary boilers; and it arises from many causes. The most frequent cause, although the most easily detected, is leakage from the joints of the fittings on the top of the boiler, which are too frequently attached by bolts instead of rivets. This evil is much increased when the boilers are covered with brickwork, which holds the water against the plates, and hides the mischief from observation. ”

“ As such corrosion usually occurs on the upper side of traps or horizontal pipes, it is not easy to detect their presence from the absence of leakage, and the only safeguard is to avoid carrying waste or soil pipes horizontally; also, to extend their upper ends through the roof, and leave them open for ventilation. Lastly, to substitute iron pipes for lead wherever possible, which is now the general rule in all good plumbing practice. ”

“ Many boilers are so set that the brickwork of the flues is made to follow the shape of the boiler, with as little space between as possible; but the slight advantage gained in increased heating effect is far outweighed by the impossibility of getting into the flues for examination. It is only by having the flues sufficiently roomy that proper examination can be made, and that the indications on the brickwork of leaking can be seen and remedied, and corrosion arrested. A remarkable case of corrosion occurred in a boiler with an oval shell, set upon a middle wall. ”

“ There is sufficient oxygen present for corrosion. This a conservative approach to corrosion. The concrete vault begins service approximately 100 days after casting. Therefore, the transport properties have reached about 90% of their assymptotic values. The external ion concentration and hydraulic head are constant over the life of the vault. As the sulfate front advances, the concrete in its wake can be treated like soil and the external conditions can be advanced to this point. ”

“ While not as strong as steel pipe under hydrostatic test, many pipe users insist that, presumably on account of its slag enclosures and cinder films which are supposed by some to surround and protect the fibers, wrought iron pipe outlasts steel pipe when used under conditions which induce corrosion. Others are as strenuous in their denial of this assertion and this subject of comparative wrought iron pipe and steel-pipe corrosion is still a very live issue. ”

“ After complete corrosion, the white lead is ground, floated, and dried. Corroded white lead has a specific gravity of 6.8 and contains about 85% lead oxide and [43] 15% of carbon dioxide and water. Its opaque nature and excellent body renders it extremely valuable as a constituent of paints. Checking and chalking progress rapidly when the pigment is used alone. The various sized particles, both large and small, resulting from the corrosion process, are prominently shown in the photomicrograph. ”

“ At all events it is necessary to beware of being misled by the terms erosion, corrosion, and the like, which all convey the idea of a chemical action; while it is well ascertained that a chemical action either does not exist at all between arsenic and the animal tissues, or, if it has existence, tends to harden and condense rather than to dissolve or corrode them. Arsenic is not a corrosive.
Another species of destruction of the coats of the stomach, which will require a little notice, is sloughing or gangrene. ”