EFHSS Questions and Answers - Question Q00709

I am responsable for two different sterilisation units in two different hospitals.

I have following strange problem: in one of these units many of the aluminum instruments or the aluminum parts of them, lose there "paint" and they are becoming a "rough" aspect. They dont have this smouth feeling anymore when you take them between your fingers.

In both sterilasation units whe use the same washing machines (Miele 7735 CD) the same chemical products Suma Med Super LHP and the neutraliuser Suma Med U.
In the ultrasonic cleaner we have 3E-Zyme (Medisafe).
The waters is tested several times and whe find nothing that can be the reason of this discoloration.
At last I can say that some people suggest that this find his reason in a steris steriliser unit because of the peracetic acid used in these devices but some aluminum object that where never in this steriliser (for exemple the Acufex sliding base 014411) also are discolorated.


So, we have this problem only on 1 sterilsation site and that is for us at the moment a kind of mystery.

Any suggestions, tips, solutions etc... are welcome

Jef, you have solved your problem yourself. The only thing is what you have noticed... can you convince this to the other parties. Things are more simple that you think and 99% of the things you have to deal with at a OP/CSSD have to do with chemical/ physical laws. You or I can't change them, so we have to use them...
rgs
Peter

You speak to me in riddles.
I don't understand...

Jeff, I am not sure what you have been told why your aluminum items are discoloring and the anodized coatings are being damaged. I have heard some detergent manufactures tell their customers that it is the water and other things. I am a chemist with over 30 years experience. I have worked with many detergents and delt with the same issues you have. Believe me it is not the water (chemically imposible), it is the detergents and I know why. If you and others in Europe will be patient, the products you need to eliminate this problem and others I have heard of lately in Europe will be available later this year. We are trying to find a reputable and large enough manufacturer to work with in Europe to manufacture our line. Please be patient, help is just around the corner. Best Regards, Sherwood

Jef,

the phenomenon you have experienced might originate from the fact that the chemicals you use do not work at a neutral pH value (around pH 7).

Acid as well as alkaline products affect and alter the surface of aluminium. This does not only concern aluminium, but also other non-ferrous or anodized metals.

For this reason, we recommend Bodedex® forte (manual) or Korsolex® Endo Cleaner (washer disinfector) for cleaning as well as our Korsolex® disinfectants (manual or washer disinfector) for reprocessing of aluminium parts / instruments.

Best regards

BODE CHEMIE HAMBURG
Annette Rittich

Dear Annette,

thank you for your reply.
we are a step closer to a solution .
But...your reaction to my question has no solution why it happends only on 1 sterilisation site (the other site is 5 km away).
the answer to that must be in my water quality? The machine? The % of the products in this machine...

Why only on 1 sterilisation site...
I am not a chemist... maybe the answer is closer than I think, but I need a chemist for the final solution I think.

Annette & Jef,

Here are the facts about aluminum. When aluminum is new and still shiny it has not been exposed to the atmosphere very long. Over time even mild acids like carbonic acid (CO2 + H2O) gives it a dull look. That is aluminum oxide. That aluminum oxide is an excellent protective coating and is very resistant to all but the very strong corrosive chemicals. Anodized aluminum is aluminum that has been treated to give it a much thicker aluminum oxide coating than normal. The chemicals that harm this coating can not be given a general grouping of acids and bases or alkaline or anything other than pH 7. The chemicals are the corrosives like sodium and potassium hydroxide and peracetic and hydrofluoric acids. Aluminum oxide is what sapphires, rubys and many other gem stones are made of. Hydroxides are but a few of the chemicals that make solutions have a pH greater than 7 and most don't harm any metals. A pH of 7 is not the ideal pH of a cleaning solution. Slightly higher is the best, but it is what you use to get that slightly alkaline pH that makes the difference. This is especially true with enzymatic detergents. I am not for sure what you mean by "paint" on the aluminum instruments. But the only other cause for roughness on aluminum is scratching and possibly too much detergent (if it is peracetic acid or have other corrosives). Scratching removes the oxide coating and will start the oxidation process all over again. Over time this causes a rough feeling on the aluminum item and slowly errodes the item. I would check to make sure both washers are set up exactly the same and if they are truly delievering the same amount of detergent. Than I would check out the washing action inside the washer during the washing cycles to see if the instruments are held stationary or being moved around (causing rubbing) in one more than the other. From another direction, is the operator always the same or do both washers have several different operators?

Best Regards,
Sherwood

Jef how can it have anything to do with the water? Both washers are using the same water source.

Sherwood

Dear Jef,

According to what you say, if you only have damage in one site, you should try two things:

1. Make sure that the same detergents are connected to the same dosage pumps.
2. Check that dosage quantity, temperature, and exposure time in each phase of the cycle are the same (Especially the temperature!).

If it is all the same- you should look elsewhere (not in the WD) for the problem.

Good luck!
Noam

Dear Jef and Sherwood

The German “Working Group Instrument Preparation” have investigated colourless anodized aluminium and coloured anodized aluminium of medical devices regarding the behaviour towards different process chemicals for reprocessing of medical devices and towards different water qualities.
With this answer I will explain the influence of different water qualities to anodized aluminium.
At first, my statement which is proved by al lot of experiences and investigations: Deionized water at high temperatures of 60° to 90 °C will protect and stabilize anodized aluminium surfaces. On the other side, softened water at 60° to 90 °C will destroy the anodized surface. The reason for that is as follows:
Softened water is produced by ion exchanger and Calcium and Magnesium salts are changed to Sodium Salts. Softened water has a high content of Sodium hydrogen carbonate. If this water is heated up Sodium carbonate will come into existence. So heated up softened water has an alkaline pH-value. The higher the carbonate hardness of water the higher the alkalinity of the produced softened water.

Enclosed you will see results of test washings:

Material:
Blue anodized aluminium specimen of company Aesculap, Tuttlingen which are the same as Aesculap containers.

Washer Disinfector:
Miele G 7735

Washing program:
Water was heated up to 93 °C for ten minutes without any process chemicals

Water Qualities:
Deionized water and softened water

Softened water:
1 time washed: 74 %
5 times washed: 27 %
10 times washed: 2 %

Deionized water:
1 time washed: 99 %
5 times washed: 86 %
10 times washed: 93 %

The thickness of the brand new aluminium oxide layer was 15 µm, expressed with “100%” in this chart. After one wash cycle with softened water the thickness was reduced and after some more washing cycles Aluminium oxide layer was completely removed with softened water.

On the other side, deionized water will protect the Aluminium oxide surface, the layer becomes more compact which was shown by additional measurement of the electricial conductivity.

More interesting results we found out with combinations of different detergents dissolved in different water qualities.

Dear Sherwood, the behaviour of anodized aluminium against different water qualities and against different detergents is more complicated as you describe in your statements. Examples: We can wash anodized aluminium in a washer disinfector with a washing solution of pH between 10 and 11 without any problems due to the inhibitors like silicates in cleaning agents, but using another washer disinfector which works with a pH neutral cleaning agent we can have problems with anodized aluminium due to the softened water. Some washer disinfectors have built in water softener, some not. Sometimes washer disinfectors are feeded with normal hard tap water, sometimes with softened water or deionized water. This is quite different and should be investigated in each case, when anodized aluminium is harmed.
Dear Sherwood,
even with 30 years of experience as a chemist you should never give up learning, same for me with 26 years of experience as a chemist.
Please have a look at http://www.a-k-i.org

I didn't bring that up because I have not seen any hospitals use softened water by way of a water softener using sodium chloride as the softener. I suspect though that if a water softener is used with NaCl as the softening chemical the biggest problem will be rusting of the SS instruments from residual NaCl. Like I said before, the pH is not the problem, it is the chemicals in the detergents or in this case, the softened water. With sodium and calcium carbonates at high tempertatures they would tend to give off CO2, creating carbonic acid and CaOH & NaOH. Again the real problem is the strong 1 & 2 group hydroxides. That is why the problem occurs at the elevated temperatures. Anodized aluminum is very simular to glass. It takes a very strong acid like hydrofluoric acid and strong hydroxides to react with either. The hydroxides take a lot longer to react at normal termperatures but react much faster at elevated temperatures. I have to deal with this issue every day. Deionized water is just that, water with no ions which can have therefore no stablizer or stabilizing effect. It just has nothing available to react with the aluminum oxide. That is why clean rain water will not harm aluminum siding (the siding already has a protective aluminum oxide coating). Sorry, but I am very versed in the properties of aluminum and will be very willing to explain the reasons, chemically, for any issues concerning aluminum and aluminum oxide.

Regards,
Sherwood