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Your first-line-of-defense against Preventing the Corrosion of Surgical Instruments is the "passive oxide layer" of Surgical Instruments.
Stainless steel surgical instruments are made of corrosion resistant high-grade specialty steels. The keyword is “resistant”. Corrosion resistant does not mean corrosion proof. One of the special characteristics of these surgical instrument steels is that the manufacturer forms a "passive oxide layer" on the surface of surgical instruments which protects them against corrosion. This makes surgical instruments as corrosion resistant as possible. It is imperative that you maintain the passive oxide layer to prevent corrosion and maintain your surgical instruments in optimal condition. If this is not done the stainless steel will be more susceptible to corrosion, pitting and stains.This will reduce the life of the surgical instruments and/or render surgical instruments useless. Initially, all “stainless steel” surgical instruments have the same corrosion resistance. When strength and hardness requirements are important factors for instrument function, corrosion resistance is generally lower. Increasing the corrosion resistance softens the stainless steel. Manufacturers of surgical instruments and surgical instrument containers recommend the use of neutral pH Surgical Instrument Cleaners. Newly developed neutral pH all-in-one or "combination detergent" Surgical Instrument Cleaners have been shown to be effective in optimizing the efficacy of the "passive oxide layer". This will provide a longer life for stainless steel surgical instruments. Surgical Instrument Cleaners with a high or low pH have been shown to erode the passive layer. The most common of these surgical instrument cleaning concentrates utilize an alkaline detergent with an acid neutralizer. All manufacturers of surgical instruments and surgical instrument containers recommend against using these detergents and recommend using neutral ph Surgical Instrument Cleaner. More information and studies regarding the "passive oxide layer" of Surgical Instruments and the value of using a neutral ph Surgical Instrument Cleaner is below.
Yellow-brown to dark-brown stains or spots on surgical stainless steel instruments are frequently mistaken for "rust". These residue deposits (stains or spots arranged in groups or along edges or in crevices) are usually the instrument being exposed to result of high chloride content. They will lead to pitting of the surgical instrument surface if not removed. (see Avoiding High Levels of Chloride below) Excessively hard water can contain high levels of salt sufficient to cause stains or spots that appear as rust. Boilers used to generate the steam for steam sterilizers, if not cleaned properly, will produce contaminated steam which can deposit minerals onto instruments during the sterilization process. Some Surgical Instrument Cleaners contain agents to soften hard water and eliminate spotting.
Avoiding High Levels of Chloride
- dry and cool instruments as soon as possible following cleaning & sterilization treatments
- whenever possible use purified water (DI or RO) to thoroughly rinse instruments prior to drying & sterilization
- avoid exposing the surface protective layer of the instrument to abrasive conditions & treatments
- minimize the time instruments are exposed to high temperatures
- avoid using agents containing chloride (do not exceed ~ 120 mg/l, 200mg/l NaCl Sodium Chloride - Salt). A common problem is the inadvertent use of NaCl Sodium Chloride - Salt containing solutions do 'soaking instruments in surgery to maintain hydration of debris and prevent encrustation.
Virtually all manufacturers of surgical instruments, rigid scopes, flexible scopes, and instrument containers recommend the use of a neutral pH Surgical Instrument Cleaner. Generic Example of this recommendation: "Do not use high acidic (pH <4) or high alkaline (pH >10) products for disinfection or cleaning, since these can corrode metal, cause discoloration or stress fractures."
Do not use abrasive pads or an abrasive Surgical Instrument Cleaner , which will scratch the surface allowing dirt and water deposits to collect. Abrasive cleaning will remove the protective passive layer.
Do not use a Surgical Instrument Cleaner with high concentrations of chlorine bleach to clean or disinfect stainless steel instruments, as pitting will occur. Never use bleach to clean any surgical instruments. The high pH of bleach causes surface deposits of brown stains and might even corrode the instrument. Even high quality stainless steel is not impervious to an acidic bleach solution. Sort surgical instruments by similar metal for subsequent processing so that electrolytic deposition (galvanic corrosion) due to contact between dissimilar metals will not occur.
Tap water can contain many minerals, which may discolor and stain surgical instruments. It is recommended that de-ionized water be used for the final rinsing to prevent spotting. all-in-one or "combination" Surgical Instrument Cleaners can be effective in treating unacceptably hard source water and removing hard water encrustation from surgical instruments and equipment. If untreated tap water is used for final rinsing, then the instruments must be dried immediately to avoid staining.
Clean instruments, or apply treatment to prevent the drying and encrustation of debris, as quickly as possible after use. Do not allow blood and debris to dry on the surgical instruments. If cleaning must be delayed, place groups of surgical instruments in a covered container with appropriate enzyme-detergent Surgical Instrument Cleaners or apply an enzyme-detergent foam spray to delay drying. The use of pre-soaking enzyme-detergent Surgical Instrument Cleaners have been shown to reduce the time expended for manual cleaning surgical instruments and render higher quality cleaning outcomes. After surgery, open all surgical instrument box locks and disassemble surgical instruments with removable parts. This will limit blood drying on surgical instruments that may cause surgical instruments to corrode. The "all-in-one" Surgical Instrument Cleaners and the enzyme-detergent Surgical Instrument Cleaners deliver a chemical complex to: maintain the hydration of bioburden, prevent surgical instrument corrosion, clean the surface of surgical instruments, and condition the surface of surgical instruments & scopes. This can significantly reduce manual cleaning and facilitate cleaning the surface of surgical instruments, scopes, and the lumens of cannulated surgical instruments inside-and-one. If used properly, all-in-one enzyme detergent Surgical Instrument Cleaners and/or all-in-one "combination" Surgical Instrument Cleanerss can render excellent outcomes and facilitate cleaning surgical instruments and scopes inside-and-out. They effectively clean the surface of surgical instruments while cleaning lumens and working channels. This can eliminate or reduce the manual labor expended, rendering lower surgical instrument reprocessing costs while improving surgical instrument turnaround.
The reprocessing decontamination process, whether done manually or automatically in surgical instrument washers decontaminators disinfectors, will be effective if pre-cleaning is adequate. Presoaking with neutral pH enzymatic detergent surgical instrument cleaners will effectively remove debris and has proven to be an acceptable alternative to manually cleaning surgical instruments. During cleaning all surfaces of surgical instruments must be exposed to the cleaning process. The use of automated surgical instrument washers may reduce the risk of exposure to contaminants, improve turnaround time, and extend the life of surgical instruments. Delicate surgical instruments may be washed manually. Surgical instrument washer decontaminator racks have been designed to safely clean surgical instruments, including delicate surgical instruments and cannulated eye surgical instruments. These Surgical instrument Washer Racks clean the surgical instruments inside and out thereby eliminating the need for manually cleaning cannulated surgical instruments.
Sterilizing surgical instruments that are inadequately cleaned instrument is not possible. Cleaning surgical instruments is the prerequisite for sterilizing surgical instruments.
Ultrasonic cleaners are more effective when used with hot water, as per the manufacturer’s recommended temperature.
It is recommended that all visible debris and blood be removed from the instrument prior to ultrasonic cleaning. Sort instruments by similar metals to prevent corrosion due to the contact of dissimilar metals. (electrolytic deposition - galvanic corrosion) It is not recommended to clean plated instruments in an ultrasonic cleaner since the ultrasonic vibration and the presence of other sharp instruments may crack or rupture the plating. Because Ultrasonic Cleaners do not provide the complete "proper sequence of treatments" i.e. final rinse(s) that are purified, purged between treatments, and/or have temperatures elevated to disinfection levels, they are not considered to be as clinically effective as automated surgical instrument washers. Ultrasonic Cleaning can effectively remove: long term encrustation and surgical cements or glues that have dried onto instrumentation.
• surgical instruments being cleaned must be fully immersed
• hinged surgical instruments must remain open during treatment
• only use cleaning trays that do not obstruct the ultrasonic cleaning process or add mass (e.g. wire baskets)
• large surface bulky items such as kidney shaped bowls must be positioned not to create anechoic (shadow) zones that will block the efficacy of ultrasonic transducer waveform. Position such items vertically or put them on top of the other items.
• always sort surgical instruments by similar metals to prevent corrosion
• do not overload the ultrasonic cleaning tank with excessive mass as this will reduce the efficacy of cleaning
• the soil being removed from surgical instruments being cleaned adds to the mass within the tank and decreases the efficacy of the ultrasonic cleaner. Review the level of soil and renew the ultrasonic bath as needed
• ALWAYS follow ultrasonic cleaning with separate rinse treatments. Ultrasonic cleaning will fragment and loosen soil but will not necessarily remove the soil from the surface of the surgical instruments being cleaned.
To maintain moving parts and protect surgical instruments from staining and rusting during sterilization and storage, surgical instruments should be lubricated with a water-soluble, preserved lubricant after each cleaning. Most automated surgical instrument washers decontaminators provide the option for lubrication at the end of the final rinse treatment. Since effective ultrasonic cleaning removes all lubricant, re-lubrication is important. "all-in-one" Surgical Instrument Cleaners will provide lubrication. The lubricant should contain a chemical preservative to prevent bacterial growth in the lubricant bath. The bath solution should be made with de-mineralized water. A surgical instrument lubricant containing a rust inhibitor helps prevent electrolytic corrosion of points and edges of surgical instruments. Immediately after cleaning, surgical instrument should be immersed or rinsed for 30 seconds and allowed to drain off, not wiped off. A lubricant film will remain through the sterilization to protect surgical instrument during storage.
Staining and spotting may result if residual chemicals are not completely rinsed from surgical instruments that are subjected to steam sterilization. Following the manufacturer’s recommendations for the proper sequence of treatments (cold water pre-wash, enzyme-detergent wash, purified water rinse/lubrication, and drying) is critical to prevent stains and spots on surgical instruments. A Surgical Instrument Cleaner that will avoid spotting is called "free-rinsing" or "rinse clean".
Studies regarding the "passive oxide layer" of Surgical Instruments
(Guidelines on metals and alloys in contact with food; Council of Europe; published 11.10.2000. Systemic nickel: the contribution made by stainless steel cooking utensils; Contact Dermatitis, Volume 32:2, 1994) of the stainless steel passive layer to prevent corrosion have revealed a reduction in corrosion prevention with the use of cleaning concentrates that are not neutral pH.
The use of Surgical Instrument Cleaners that deliver an acid rinse will release nickel from the stainless steel and decrease the efficacy of the surgical instruments passive layer. This is most critical on initial reprocessing events of stainless steel surgical instruments. Measurable levels of nickel have been detected. It was also shown that, as the number of subsequent uses increased, the level of nickel release diminished and reached a steady state (measured in the order of μg/l). These observations reflect the changes that occur in the passive oxide layer of surgical instruments on first immersion of stainless steels in aqueous media.
What is a Stainless Steel Surgical Instrument ?
Stainless steel is essentially a low carbon steel which contains chromium at 10% or more by weight. It is this addition of chromium that gives the surgical instruments steel its unique stainless, corrosion resisting properties. The chromium content of the surgical instruments steel allows the formation of a rough, adherent, invisible, corrosion-resisting chromium oxide film on the steel surface. If damaged mechanically or chemically, this film is self-healing, providing that oxygen, even in very small amounts, is present. The corrosion resistance and other useful properties of the surgical instruments steel are enhanced by increased chromium content and the addition of other elements such as molybdenum, nickel and nitrogen. Stainless steel has a passive film created by the presence of chromium (and often other alloying elements, nickel, molybdenum) that resists this process. When exposed in air, surgical instruments stainless steels passivate naturally (due to the presence of chromium). But the time required can vary. In order to ensure that the surgical instruments passive layer reforms rapidly after pickling, a passivation treatment is performed using a solution of nitric acid and water.
The passive layer or stainless steel is intended to prevent or resist surgical instrument corrosion. The process is called “Passivation”. “Passivation” and Polishing eliminate the carbon molecules form the instrument surface. This forms a layer which acts as a corrosive resistant seal. Passivation is a chemical process that removes carbon molecules from the surface of the surgical instruments. This chemical process can also occur through repeated exposure to oxidizing agents in chemicals, soaps, and the atmosphere. Polishing surgical instruments, by the manufacturer, is a process used to achieve a smooth surface on the surgical instruments. Surgical Instruments are polished because the passivation process leaves microscopic pits where the carbon molecules were removed. Polishing also builds a layer of chromium oxide on the surface of the surgical instruments. Proper cleaning, handling, and sterilization of surgical instruments will build up the layer of chromium oxide and protect the Surgical Instruments from corrosion and /or pitting. In some circumstances older surgical instruments have higher resistance to corrosion than new ones. The newer surgical instruments have not had the time to build up the chromium oxide layer. Improper cleaning and sterilization of surgical instruments can cause the layer of chromium oxide to disappear or become damaged thus increasing the possibility of corrosion and/or pitting. Proper cleaning and sterilization of surgical instruments can cause the layer of chromium oxide to improve over time thus decreasing the possibility of corrosion and/or pitting. Second only to the financial asset value of the working staff, the surgical instrument and scope inventory is the single most financially valuable asset of the healthcare facility. It is important to properly clean, sterilize, handle, and store your surgical instruments.
John Temple
Product Development
will lower your cleaning costs and replace cleaning products for:
