The comparatively availability of different types of material such as concrete, rubber or metal having favorable physical and chemical properties for use in the gold ore processing plant has made the operator´s life much easier and construction and maintenance costs cheaper. One of the materials employed in the plant construction is concrete, which is slowly attacked by many of the solutions commonly found in gold processing plants, and effective protection of floors and foundations at reasonable cost is possible by selecting the suitable concrete and necessary additives. For example acid compounds will cause the lime content of the cement binder in concrete either to be leached out or to form calcium sulphate. These reactions by increasing the porosity and by causing swelling with mechanically weaken the concrete surface causing spalling and general deterioration. Similar effects are produced by continual contact with sulphates, carbonates and other salt solutions. The best protection against this type of attack, short of surfacing with protective materials, is to provide for good drainage with as even a surface as possible. The recommended overall floor slope in areas susceptible to corrosion is at least 15 mm per meter and depressions are ordinarily less than 4 mm deep in a 2.40 m span.
A properly designed concrete mix, made with water having a low dissolved salt content, and which good placement technique will give a prolonged floor life in mildly corrosive conditions. Nevertheless, densification through the use of additives must be studied carefully. With more corrosive conditions it is feasible to consider a especial cover on the concrete with any of a number of available materials ranging from special paints to a complete resurfacing with corrosion resistant bricks and tiles. It has been noted that coatings of 5 to 140 mils thickness are fairly successful under moderately severe conditions. Monolithic surfaces from 2 to 4 mm thickness have been highly successful if properly chosen and properly applied, although installation costs could be a little high. Also concrete tanks and vat linings in severe physical service under corrosive conditions need special design; otherwise they could collapse slowly.
Some gold concentration equipments or reagent preparation systems are made of stainless steel. Probably, type 316 stainless steel is employed for many applications where both good corrosion resistance and the physical characteristics of a metal are needed. Stainless steel is corrosion resistant in oxidizing environment due to the formation of a passive surface film. Exposure to either active reducing agents or to severe abrasion will tend to destroy this layer and will lead to increased corrosion rates. This effect is minimized in type 316 stainless steel as a result of the addition of a small amount of molybdenum to the alloy. If welding is required, a so called stabilized stainless steel must be employed in order to avoid susceptibility to localized corrosion in the vicinity of the weld. The stabilized alloy contains niobium or titanium as additives or may have decreased carbon content. Type 316 resists corrosion by sulphuric acid in concentration up to 5% and temperature up to 50oC. Higher acid concentrations are possible at lower temperatures. The presence of small amounts of chloride or sulphides may increase the corrosion rate, which may continue even in normally non-corrosive solutions until steps are taken to repassivate the metal by restoring the protective surface film. This can be done by rinsing the metal with a strong oxidant such as a solution of nitric acid. RIP screens constructed with high alloy content stainless steel show increased resistance to corrosion of the pitting and electrochemical type.
Other important material is rubber. Basically, synthetic rubbers are employed for both corrosion and abrasion resistance in many applications. Rubber lined pipe and rubber hose are employed in several parts of the plant and are particularly good where abrasion resistance is important. Rubber may be employed to cover nearly any desired surface and is applied as sheets formed to fit the required contours with suitable adhesives. Cold cementing or pre-vulcanized sheets may be used to cover areas where abrasion resistance is the only requirement. For proper corrosion-proofing, however the rubber is applied in unvulcanized form and then heat-cured in place. The surface to be covered must be free of cracks and pits and must be dry and clean to achieve complete bonding without blistering.
Adsorption system covered with stainless steel Ball mill area must reinforced with steel and concrete