Rusting can be prevented in order to maintain the value of the object. Cathode Protection: This is the method of protecting iron from rusting by connecting it by wires to a more reactive metal such as magnesium or zinc.
This method is used when dealing with underground metallic pipelines and tanks. Herbert J. Kaiser, PhD; Patrick Schwab, MBA; Jason F.
Surgical instrument spotting, staining, and corrosion are serious problems in many healthcare facilities. These problems can be avoided provided careful attention is given to the method of processing the instruments and possible causes are understood.
This article covers various reasons to monitor the instrument-processing scheme along with understanding basic instrument construction itself. Stainless steel is composed of iron, carbon, chromium, nickel, manganese, silica, and many other metals in smaller quantities.
The amount of chromium and iron oxide varies depending on the type of stainless steel (e.g., 410, 416, 316, etc.). When these parts are exposed to air, the chromium and iron present in the stainless steel are oxidized.
A more passive layer is than formed by treating the parts with chemicals that remove some iron from the surface but leave the chromium behind. Chromium is the principal metal responsible for the passive behavior of stainless steel.
Scratches to the passive layer can occur either through improper handling of the instrument or through normal usage. While detainees are necessary in some cases to remove some areas of corrosion and tough stains, they should not be used on a daily basis, as this will eventually erode the passive layer, making it thinner and providing less protection.
Soil residues that are allowed to dry on the surface of instrument scan cause damage to the passive layer. This can occur when instruments are allowed to soak overnight in strong disinfectant solutions.
Exposure to chlorine compounds like bleach is very detrimental to the stainless steel surface. Stainless steel should never be exposed to chlorine for extended periods nor soaked in sodium chloride solutions.
A common practice in some operating rooms is to immerse stainless steel instruments in saline solutions. Exposure of instruments to either chlorine or sodium chloride is one of the most harmful things that can be done to stainless steel.
An often overlooked source of staining or damage to the passive layer is residues from reusable instrument wraps. It is important to understand the process by which these reusable wraps are cleaned in order to be aware of potential sources of damage to surgical instruments.
In a commercial laundry, where instrument wraps are normally reprocessed, a totally different process occurs. This laundry sour neutralizes any alkalinity remaining in the wraps from the detergent.
This alkaline residue can then be reactivated under the high-temperature and humidity conditions of a sterilizer and leach onto the instruments, causing them to become stained or corroded. Also, if there is overall improper rinsing of the wraps, surfactant residues can be left in the linens.
If the wraps are suspected of causing staining of the instruments they can easily be checked for laundry residues. There is a simple test to determine if the wraps are alkaline or acidic in nature.
This involves boiling deionized water and determining its initial pH. Additionally, if the water is foamy after boiling the wrap, there may be detergent residues present.
If the linens are found to be acidic, alkaline, or if there are detergent residues present, the laundry should be consulted to make sure proper procedures are being taken to avoid and eliminate these problems. This occurs primarily because of the rapid temperature change that the surface experiences during flash sterilization.
Instruments generally are not physically or chemically affected by spots if they are removed. The use of high-quality cleaning chemicals can avoid mineral deposit formation during the wash cycle.
The use of cleaning chemicals outside the recommended dilution rates may also cause spotting. Equipment should be maintained so that the appropriate amounts of cleaning chemicals are fed into the washer.
This can be done by making sure that the steam and boiler water are monitored on a regular basis. Additionally, steam lines should be flushed after any major adjustments to the boiler.
Spots resulting from poor soil removal can be avoided through the use of high-quality cleaning chemicals. The use of enzyme presoaks is recommended for initial protein soil removal.
In contrast to spots, stains are tightly adherent deposits on the surface of instruments. However, as with spots, the instruments generally are not physically affected by the presence of the stains.
In addition, the stain can appear as a gold or rusty tint on instruments. This can be avoided by segregating dissimilar metals and washing them at different times.
When this is the case, a cleaner that is safe on soft metals (e.g., brass, aluminum, and copper) can be used to minimize the effect. To avoid staining caused by disinfecting solutions, the soak time should be limited (i.e., follow label directions closely).
A common stain seen after sterilization is a rainbow or bluish appearance on instruments. This typically is caused by the presence of an excessive amount of neutralizing amines in the steam.
However, an excessive amount of neutralizing amines can be prevented by working closely with the boiler operators. The stains encountered in these washers are typically either black or rust in color.
The black color is a result of the alkalinity of the detergent not being sufficiently neutralized. To avoid discoloration of the instruments in these systems, it is important to ensure that alkalinity is being properly neutralized.
Herbert J. Kaiser, PhD, is a principal scientist at Sterns Corporation. He has 17 years of experience in cleaning technologies and is the sole inventor listed in five US patents for various industrial treatment schemes.
Jason F. Tire, MA, is a scientist at Sterns Corporation with two years of experience in cleaning and surface technologies. Patrick Schwab, MBA, is a product director, marketing, at Sterns Corporation with 14 years of experience in healthcare.
Because of the ferrous metal (iron) used on early blades, collectors often encounter rust and corrosion. Thus, to try to bring artifacts back to their “as new” appearance is often damaging to the object and detracts from its value.
If active corrosion is present, store in a dry environment (relative humidity less than 35 percent). Use silica gel desiccant products to reduce humidity in storage container, if necessary.
Then wipe with a cloth dampened with mineral spirits (again, be careful with plated surfaces). You will merely damage the surfaces and possibly remove important information such as manufacturers stamps.
Wipe blades lightly with machine oil to protect them from further corrosion. Consult a conservator for cleaning instruments with unstable plated or painted blades or handles.
The nails are placed in test-tubes and covered with corrosion indicator solution. The indicator changes color from yellow to blue to show where rusting is taking place.
By comparing the amount and position of the blue indicator on each nail, the effectiveness of the different types of protection can be assessed. They can paint the nails, cover them in plastic, wrap them in another metal and so on.
This can be achieved with dilute (about 1 M) hydrochloric acid, followed by thorough rinsing in cold water. Cooking oil is probably the easiest to use.7 Prepare the corrosion indicator shortly before the lesson as it does not keep well.
Make a warm solution of 5 g gelatin in 100 cm 3 water and then dissolve 0.2 g potassium hexacyanoferrate(III) in it. Keep the solution warm but not hot, otherwise toxic gases can be evolved.
If you have access to one, a magnetic stirrer with hotplate is ideal for this but it is not essential. Wrap one nail in thin plastic film, such as ‘clingfilm’.
Wrap a small piece of magnesium ribbon or zinc foil around a section of a nail. Wrap a small piece of copper foil around a section of a nail.
Place a stainless steel nail, bolt or screw into a test-tube. C Carefully pour the corrosion indicator into each test tube, completely covering each nail.
After about half an hour it will be possible to see the indicator changing from the starting yellow color to dark blue in patches on the nails. These dark blue patches indicate areas where rusting is starting.
Initially iron goes into solution as Fe 2+ ions, losing electrons: The Fe 2+ ions combine with the indicator to form a blue solid.
This indicator will show the cathodic areas as well, as the hydroxide ions cause the phenolphthalein to turn pink.) For more detail on the reactions involved in the rusting process, see the website below.
The magnesium donates electrons to the iron, which slows down the rusting process. The other nails will rust in a variable way, depending on how effectively they have been coated.
Alloying is also an effective method of rust prevention and chips and scratches in the surface are generally not important. As a result, the stainless steel nail will generally not rust much, if at all.