Stainless steel is the metal used most often for surgical instruments because the metal is strong, can withstand extremes in temperature and resists rust. The primary ingredient in pure steel is iron ore, which loves oxygen. Therefore, ordinary steel easily rusts and corrodes; the metal can eventually be eaten away. To guard against this, manufacturers add ingredients to make steel ‘stainless’ and impede corrosion. One such ingredient is carbon and another is silica, which helps to withstand high temperatures. Manganese, sulphur and phosphorous also provide additional strengths. However, the addition of chromium is the true key to making surgical stainless-steel instruments long lasting. When chromium and oxygen come into contact with each other, a natural chemical reaction creates a protective coating call chromium oxide, which prevents rusting. Chromium oxide is a clear, almost invisible substance; most of us don’t realise it’s there.
In order to achieve this protective coating, the following processes must be completed: passivation and polishing. Passivation is a process in which nitric acid is used to remove free carbon and free iron that may remain on the surface of the instrument. This is a chemical method of accelerating oxidation. The result is the previously mentioned chromium oxide layer, which helps to preserve the integrity of the instrument. The final step is to polish the instrument. Different types of finishes may be provided on surgical instruments: a shiny finish or a matt finish. The latter is created by bombarding silicone beads against the surface to create a dull finish. Such beads do not penetrate the chromium oxide layer created by passivation.
Actions in the clinical setting can harm an instrument’s protective chromium oxide coating. Once that layer is broken down, the stage is set for corrosion to begin. For example, alkaline and acid cleaning chemicals can compromise an instrument’s protective coating. Both can be found in washer disinfectors used in some sterile services units and chemical solutions used in the operating theatres. Salts are among the biggest culprits in corroding surgical instruments. When salt is put on a metal and left for a period of time, corrosive action or pitting begins; salt literally eats away the passivation layer of the instruments leading to rusty-looking corrosion appearing on instruments before actual pitting begins to show, but these can sometimes be mistaken for water spots. If instruments appear spotted after the decontamination process water spots will rub off; corrosion will not. If corrosion has begun, under magnification you will be able to see a small pit beginning to form.
It is very important that the detergents used to clean and wash instruments are carefully considered. Neutral detergents have a pH, which usually falls in the range between 6.5 and 8.0. Water, which is considered neutral, has a pH of 5. Acids range from 1 to about 4.5 pH. On the other hand, the alkaline range is from about 8.5 up to 14pH. In choosing detergents attention must be paid to the pH factor, is a detergent is too acidic, it will start corroding instruments’ chromium oxide layer. The same applies if a detergent is too alkaline.
Although Surgistain cannot repair the damage, it will remove the rust stains, spotting and corrosion, and all mineral staining frequently encountered from disinfection and sterilisation. Surgistain helps loosen stiff joints and locks.
It is recommended that a routine preventative program be initiated using Surgistain monthly. Routine use of Surgistain will enhance the life and efficiency of stainless-steel instruments without harming them.
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