SILVER

A Corrosion Comparison of Agricultural Disinfectants on Metals

A comparison of the corrosive nature of five commonly used agricultural disinfectants on a variety of metals used in food processing facilities, farms and veterinary clinics.
Mark Norregaard
Grade 9

Hypothesis

1. The mild steel coupons will be the most easily corroded of the five metals tested by all five of the disinfectants. If this is true then the mild steel coupons will have the most observable corrosion and should lose the most weight in comparison to the other four types of metal coupons.

2.The disinfectant, Virkon, will be the most corrosive of the five tested disinfectants on all of the five tested metals. If this is true then the five metal coupons in the Virkon wells will have the most observed corrosion and should lose the most weight in comparison to similar metal coupons in the other disinfectants.

Picture 1: Disinfectants Used in Study

 

Picture 2: Disinfectant Dilutions Used in Study

 

Research

The agriculture industry uses many different disinfectants in food production and processing, animal health and treatment and biosecurity. These disinfectants often come into contact with metal surfaces, highlighting the need to understand which disinfectants are most corrosive on which types of metals. This allows the proper selection of disinfectants that cause the least amount of corrosion on a specific metal to preserve the metal surface for as long as possible. This is assuming the disinfectants are equally effective at killing bacteria and viruses.

The purpose of my study was to compare the corrosive nature of five commonly used agricultural disinfectants (Bleach, Virkon, Hydrogen peroxide, Isopropyl alcohol and HemaPeroxy) on a variety of metals used in food processing facilities, farms and veterinary clinics (aluminum, stainless steel, galvanized steel, mild steel and brass).

Picture 3: Metal Coupons Used in Study

 

Picture 4: Labelling Disinfectant Wells and Metal Coupons

 

Variables

Controlled Variables

  • Temperature of Disinfectants
  • Disinfectant Wells and Lids Holding Metal Coupons
  • Amount of Disinfectant in Each Well
  • Time that the Metal Coupons were in the Disinfectant

Manipulated Variables

  • Types of Metal Coupons
  • Types of Disinfectants

Responding Variables

  • Number of Corrosion Indicator Observations
  • Changes in Coupon Weights

Picture 5: Preparing Coupons, Wells and Disinfectants

Procedure

Materials: Disinfectants, Metal Coupons, Personal Safety Equipment, Distilled Water, Twelve Well Culture Plates, Pipette and Pipette Tips,   50 ml Falcon Tubes, Sonicator, Camera, Scale, Parafilm, Tweezers.

Procedure:

1. Gathered the materials and put on the personal safety equipment.

2. Weighed the metal coupons, recorded the weights, labeled the wells and lids numbering 1-75, labeled the rows of wells with B (10% Bleach), V (1% Virkon), H2O2 (3% Hydrogen Peroxide), I (70% Isopropyl Alcohol) or H (1% HemaPeroxy).

3. Placed the metal coupons into the groove lids with parafilm. In each well pipetted a total of 5 ml of the designated disinfectant.  I did three replicates of each metal/disinfectant combination. 

4. Lids with the attached coupons were put into the well solutions. The plates were left at room temperature on the counter.

5. The wells and coupons were observed and photographed five times (Day 9, 16, 23, 33, 40). Coupon observations noted any crystallization, rust, disintegration, blackening, green (patina), no change and pink discoloration. Wells were observed for the accumulation of solids.

6. On day 48, coupons were photographed, rinsed in distilled water, removed from the lids, air dried and weighed.

7. Then the coupons were individually sonicated in beakers of 2.5% acetic acid (vinegar) for 20 minutes to remove all corroded metal consistently. Coupons were dried and weighed again.

8. Visual observations and coupon weights were compared between disinfectants and metals to measure corrosion loss between the coupons starting weight and ending weight.

 

Picture 6: Weighing Metal Coupons

 

Picture 7: Coupons and Disinfectants Set Up

 

 

Picture 8: Sonicator

Picture 9:  Coupons in the sonicator

Observations

Metal Corrosion Observations

 

Mild steel (200) had the most corrosion observations followed by galvanized steel (149), brass (123), aluminum (71) and stainless steel (11) had the least corrosion observations over the five observed time points.

Figure 1: Number of Corrosion Observation Means for Each Metal in the Five Disinfectants

e.g. 9.67 on figure = 29 corrosion indicator observations for d0 to d40 / 3 replicates

 

Picture 10: Wells and Coupons Used for Observations of Corrosion Indicators

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Metal Coupon Weights

Coupons were weighed on Day 0 at the start of the experiment and then again on Day 48 after being sonicated at the end of the experiment.

 

Figure 2: Coupon Weight Change Means for Three Replicates by Metals in five Disinfectants

Disinfectant Corrosion Observations

Bleach (137) had the most corrosion observations followed by Virkon (108), H2O2 (107), HemaPeroxy (104) and Isopropyl Alcohol (98) had the least corrosion observations over the five observed time points.

Pictures 11 and 12: Stainless Steel in disinfectants V = Virkon (coupons 1-3), H2 O 2 = Hydrogen Peroxide (coupons 4-6), I = 70% Isopropyl Alcohol (coupons 7-9), H = HemaPeroxy (coupons 10-12). Before Sonication (Tray 5)

                 

•Comparing the change in coupon weights from d0 to d48 after sonication between the disinfectants showed no significant difference.

 

Disinfectant Metal Coupon Weights

Figure 3: Coupon Weight Change Means for Three Replicates by Disinfectants on five Metals

 

Analysis

Metal Corrosion Observations

Graph Pad Prism 6.02 - 1 way ANOVA test was done. When choosing which test to use to compare my data I considered the following: 

  1. Experimental design: I was comparing the means of three or more matched groups of data, in my case it was five.
  2. Test: I chose the repeated-measures one-way ANOVA test to compare the combinations of the five matched groups, which turned out to be ten different combinations; instead of the unpaired two tailed t-test because it gives Type 1 (false positives) errors on more than two groups of data

Corrosion observations were totalled up for the three replicates of the five metals in each of the five disinfectants.

  1. Mild Steel was significantly more corroded than the Stainless steel and Aluminum (P<0.05).
  2. Galvanized steel was significantly more corroded than stainless steel and Aluminum (P<0.05).
  3. Brass was significantly more corroded than Stainless Steel (P<0.05).

Metal Coupon Weights

  1. A repeated-measures one-way ANOVA test was performed to compare the coupon weights before and after corrosion between each of the combinations of metals.
  2. Change in coupon weights from d0 to d48 after sonication were significantly different between brass and aluminum and brass and stainless steel (P<0.05).

Disinfectant Corrosion Observations

A repeated-measures one-way ANOVA test was performed. There was no significant difference in the corrosiveness of the five tested disinfectants.

Disinfectant Metal Coupon Weights

A repeated-measures one-way ANOVA test was performed. Comparing the change in coupon weights from d0 to d48 after sonication between the disinfectants showed no significant difference.

Conclusion

•I accept my hypothesis 1 as true, mild steel coupons had the most observed corrosion and coupons lost the most weight compared to the other metals.
 
•There was no statistically significant difference in corrosion action between the five disinfectants however bleach was observed numerically to cause the most corrosion observations as well as the greatest loss in coupon weights.
 
•I reject my hypothesis 2 as there was no significant difference between the five disinfectants, so Virkon was not the most corrosive disinfectant.
 
•Based on these results from a corrosion perspective stainless steel would be the best metal to choose for use as a surface coming into contact with these five disinfectants.
 
•Selection of a disinfectant from a corrosive perspective on the five tested metals would support not using bleach and instead  using Isopropyl alcohol if their bacteria and virus killing capability were equal. However, cost wise bleach is $.21/L at 10% concentration and Isopropyl alcohol is $15/L at 70% so cost may play a role in the decision.
 
•In the Agricultural Industry if you have surfaces such as benches in food processing plants or veterinary clinics coming into contact with disinfectants it would be advantageous from a corrosion perspective for them to be made out of stainless steel rather than any of the other tested metals to avoid corrosion.
 
•However cost and structural durability may influence this decision
 
 
Picture 13: Stainless Steel Lab Bench
 

Application

Project Improvements:

1. Testing more types of metals and disinfectants used in the Agricultural Industry.

2. Testing different shapes of metals similar to those used in Agriculture to see if pooling of disinfectants would increase corrosion.

Further Research:

1. Extending the time that the metals were in contact with the disinfectants.

2. Applying costs to different types of metal surfaces and how long they last compared to each other to see which is the most economical based on cost versus durability.

Picture 14: Coupons after Exposure to Disinfectants

Sources Of Error

Potential Sources of Error:

  1.   Corrosion Indicator Observations are somewhat subjective.

Citations

  1. Selected Disinfectants- Biosecurity for Canadian Cervid Farms Producer Planning Guide Animal Health Canadian Food Inspection Agency. “Appendix 4: Selected Disinfectants. July 6, 2018. https://www.inspection.gc.ca/animal-health/terrestrial-animals/biosecurity/standards-and-principles/planning-guide/eng/1529933780338/1529933780826?chap=20
  2. Characteristics of Selected Disinfectants. The Center for Food Security and Public Health. 2004. https://www.cfsph.iastate.edu/Disinfection/Assets/CharacteristicsSelectedDisinfectants.pdf
  3. Metal Samples Company, “Corrosion Coupons & Weight Loss Analysis. 2020. https://www.alspi.com/coupons-intro.htm
  4. A.O.A.C. (1990) Official Methods of Analysis. 15th Edition, Association of Official Analytical Chemist, Washington DC.
  5. “Are Your Stainless Steel Surfaces Being Corroded by Repeated Bleach Use?” 2014. https://www.rdworldonline.com/are-your-stainless-steel-surfaces-being-corroded-by-repeated-bleach-use/
  6. Diane D Addie, Corine Boucraut-Baralon, Herman Egberink, Tadeusz Frymus, Tim Gruffydd-Jones, Katrin Hartmann, Marian C Horzinek, Margaret J Hosie, Albert Lloret, Hans Lutz, Fulvio Marsilio, Maria Grazia Pennisi, Alan D Radford, Etienne Thiry, Uwe Truyen and Karin. “Disinfectant choices in veterinary practices, shelters and households”. 2015 https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.861.6314&rep=rep1&type=pdf
  7. The Pig Site, “Disinfectants can cause damage to metal”, 2020. https://www.thepigsite.com/news/2020/03/disinfectants-can-cause-damage-to-metal
  8. Kennedy, Jim, Bek, Joe, Griffin, Dee. “Selection and Use of Disinfectants”. University of Nebraska–Lincoln. 2000. https://core.ac.uk/download/pdf/188054146.pdf
  9. Graph Pad Prism User Guide version 6.02 for Windows, GraphPad Software, La Jolla California USA, www.graphpad.com, 2013
  10. “Choosing a Test to Compare Two Columns”. GraphPad Statistics Guide. March 31, 2019. https://www.graphpad.com/guides/prism/6/statistics/stat_choosing_a_t_test.htm?toc=0&pr.
  11. Google. “What Happens to the weight of an Iron Bar When It Rusts”. March 31, 2019. https://www.gktoday.in/question/what-happens-to-the-weight-of-iron-when-it-rusts
  12. A.O.A.C. (1990) Official Methods of Analysis. 15th Edition, Association of Official Analytical Chemist, Washington DC.

Acknowledgement

        

                               Nick Allan *                                                  Crystal Schatz*                                                       Dr Joe Ross*

* Chinook Contract Research, technical advice and supplying the metal coupons

 

 

Dr Brenda Ralston, Parkway Research Ltd., lab materials and technical advice