1 Spots and Stains
| In nearly all cases these problems are the result of minerals being deposited upon the surface of the instruments which appear as brown, blue... colors etc. Often, yellow-brown, to dark-brown blister-like spots show on sterilized instruments are mistaken as rust. In most cases, such residue can contain high degrees on chlorides which then lead to chloride induced pitting on parts made of stainless steel if the spots are not removed immediately. So, adhering to proper technique during cleaning and sterilizing procedures will prevent most staining occurrences. The following table summarizes the causes and treatments of most common spots and stains. |
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| Stain/Spot | Problem | Cause | Treatment |
| Brown Stains | Copper Coating or Platting | Detergents containing polyphosphates | Use Neutral Detergent or check the quantities used. |
| Blue Stains | Residue Deposits | Use of cold sterilization techniques(Old sterilizing solutions) |
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| Black Stains | Caustic Reaction |
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| Bluish-Blackish Stains | Metallic Coating or Platting | Metals of different types have been sterilized together e.g.; stainless steel with Silver / Chrome / etc. | Sterilize only the similar metal instruments together |
| Light or Dark Spots | Metal Deposits |
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| Rust Deposits | Deposits | residual organic matter or mineral deposits | use of distilled or demineralized water |
| Several Colors | Excess Heat (Chromatic Oxide) | The autoclave is not operating properly or has been set to very high temperature (This can cause metal to lose some of its properties such as strength and hardness etc., etc.) |
Correct the autoclave temperature |
Conclusion
The use of distilled water, careful preliminary cleaning, using neutralized pH solutions, following manufacturer's instructions, visual inspection, will all help to keep instruments performing accurately and cosmetically free of troublesome stains.
2 Corrosion
Corrosion is the disintegration of an engineered material into its constituent atoms due to chemical reactions with its surroundings. In case of surgical instruments any kind of corrosion can only occur due to inductions of water, aqueous solutions or steam.
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How corrosion occurs
Two factors affecting corrosion resistance, the chromium and carbon contents of stainless steel. In general, the more chromium present in the alloy, the more resistant it is to the corrosion. Carbon reduces the corrosion resistant effect of chromium, but it is necessary to produce hardness. In order to minimize corrosion of these harden able stainless steel alloys, the instrument will have passed through two processing steps which increase its resistance to corrosion; Passivation and Polishing (review the production process).
Kinds Of Corrosion
The following table describes the most important kinds of corrosion and their effects, in the sequence of their frequency of appearance.
| Corrosion Type | Problem | Cause | Treatment |
| Pitting corrosion | surface holes, rust and finally destroy the instruments |
active chlorides (chloride induced pitting) or halide ions other electrochemical causes |
Clean instruments immediately after use in distilled water |
| Stress Corrosion | cracking at the joints | incorrect handling chloride involved in water |
only close the ratchet during sterilization use distilled water |
| Fretting and crevice corrosion |
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chemical or mechanical destruction of the natural passive coating of the high quality steel. *lack of sufficient lubrication |
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| Contact corrosion | rust blisters | Metallic contact of instruments and unfavorable cleaning and rinsing conditions, e.g. tap water containing chlorides or contact with non stainless steel goods, such as needles, cutters, etc. |
Manual cleaning is preferable than machine cleaning Avoid contacts with non stainless steel goods |
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Surface corrosion
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instrument rust | chemical or other electrochemical influences |
Avoid chemical or other electrochemical influences |
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resultant corrosion |
A-Transferred rust B- extraneous rust |
A-Transfer of rust particles from one instrument to another during disinfection, cleaning or sterilizing B- deposit of transport rust particles on the inside of the sterilizing chamber, on the packing, on instrument surfaces. |
A-separate corroded instruments |
Conclusion
In order to reduce corrosion, instruments must be thoroughly cleaned and dried, and they must not be given prolonged exposure to sterilizing solutions. When corrosion does occur in stainless steel instruments, it is usually of superficial nature. This surface corrosion may be removed by soaking in a solution of alcohol and ammonia or by re-polishing by the manufacturer.