WHY WE CHOOSE UNCOATED STAINLESS STEEL FOR OUR PRODUCTS
Stainless steel has one of the most green and sustainable life cycle assessments of any consumer product, even though there are environmental impacts of its production. This is especially true when it is uncoated. The need for coating, treating and lining, which is usually driven by preventing rust and degradation of metal, is eliminated by the nature of the alloy and the production process of stainless steel.
Producing stainless steel products was historically very energy intensive but increased efficiency in process technology has decreased the amount of energy required to manufacture stainless steel. Stainless steel products have the longest lifespan of any product in the spectrum of reusables (vs. ceramic, glass, plastic, paper).
These products are virtually unbreakable and are 100% recyclable. If they are improperly disposed of in a landfill, they do not contribute toxins to groundwater and soil.
The primary negative impacts derive from the mining and processing of iron (5% of the earth’s crust) and chromium. Due to the exceptional durability of the austenitic products produced from these raw materials, the impacts from the extraction are mitigated only over the long lifespan.
1) Obtaining raw materials
Stainless steel is an alloy of Iron with a minimum of 10.5% Chromium. Chromium produces a thin layer of oxide on the surface of the steel known as the 'passive layer'. This prevents any further corrosion of the surface. Increasing the amount of Chromium gives an increased resistance to corrosion. Stainless steel also contains varying amounts of Carbon, Silicon and Manganese. Other elements such as Nickel and Molybdenum may be added to impart other useful properties such as enhanced formability and increased corrosion resistance. These items are typically mined.
During production, stainless steel uses scrap metal as its primary raw material, with up to 70% of the product coming from recycled material.
2) Melting and Casting
The raw materials that constitute a stainless steel item are placed together and melted in an electric furnace. Intense heat is applied rigorously for a period of 8 to 12 hours during this step. Once the melting is complete, the molten steel is cast (moulded) into the semi-finished cup and water bottle forms.
The primary energy requirements to produce 1 metric ton of austenitic stainless steel with assumed metals concentrations of 18% Cr, 8% Ni, and 74% Fe is (1) 53 GJ, (2) 26 GJ, and (3) 79 GJ for each scenario, with CO2 releases totaling (1) 3.6 metric tons CO2, (2) 1.6 metric tons CO2, and (3) 5.3 metric tons CO2. Thus, the production of 17 million metrictons of austenitic stainless steel in 2004 used approximately 9.0 x 1017 J of primary energy and released 61 million metric tons of CO2. Current recycling operations reduce energy use by 33% (4.4 x 1017 J) and CO2 emissions by 32% (29 million tons). When stainless steel is produced solely from scrap, which is currently not possible on a global level due to limited availability, energy use would be 67% less than virgin-based production and CO2 emissions would be cut by 70%.
Stainless steel has the best ratio of durability, washability, recyclability, and sustainable lifecycle of production.
In the second stage, the semi-finished steel shapes undergo a series of forming operations.For instance, the stainless steel is hot rolled (heated and passed through rolls). The slabs on the other hand are formed into plates, strips or sheets. It is very common to turn semi-finished steel shapes into bars, as it is the most versatile stainless steel form.
4) Heat Treatment
As the name clearly suggests, the various stainless steel forms undergo a thorough annealing process during this step. Annealing is another name for heat treatment where the stainless steel is heated and cooled in a controlled environment. The purpose of this heat treatment is to relieve the pent up stress inside the stainless steel and soften the material to make it more suitable for being made into products.
During the annealing process, a certain amount of scale appears on the surface of the stainless steel. This scale can be removed using a number of different processes that are collectively known as descaling.
The semi-finished, heat treated and descaled stainless steel forms are cut into specific shapes in this step. Mechanical cutting is performed with the aid of guillotine knives, blanking, nibbling and high speed blades. Nearly all of Zoetica’s products are made from 18/8 grade stainless steel, which is the highest quality available. If the cup or bottle has a double wall like ours, it is necessary to vacuum seal the area between the two walls and then test to be sure the vacuum seal was successful
Zoetica products are typically not finished, meaning they receive no color, top coat, powder coat, color layer, art application, etc. This is because the addition of this kind of layer has extreme environmental impacts and causes a cup to need to be used 300 times to achieve break even with the energy put into a disposable paper cup or bottle. Without the finishing coat, the cup must be used only 24 times to be environmentally better than the use of a disposable cup.
Stainless steel does not cause adverse health effects or leach any toxins during use or if disposed in the landfill.
The manufacture of stainless steel has been studied extensively and there is no indication that its production adversely affects the health of workers. Grinding and cutting does not cause health effects in workers. Welding is not known to increase lung cancer.
Moneypenny, J.H.G. (1921). "Unstainable Steel". Mining and Scientific Press. Retrieved 17 February 2013.
European Standard EN 10088-1:2005 "Stainless steels - Part 1: List of Stainless steels. British Standards. 2005.
"UNS S31600 Austenitic Molybdenum Stainless Steel". MaterialGrades. 2018.