From Metalworking Production, 14 April 2003

Protect products and the environment

By Steven Cartlidge and Brian Coles

Many companies, making value-added metal components while aiming for ISO-14001 certification, do not realise that there are environmentally friendlier alternatives to the metal working fluids and post production packaging materials they are currently using.

The particular problem they face is the confusing terminology and a lack of understanding of the real - and decreasing - costs of moving towards environmentally friendlier products in their operations.

Lake Chemicals and Minerals has been working with engineering companies in the UK and Ireland for a time to try to understand their needs for corrosion protection.

However, this is a topic of general interest and few suppliers provide a range of products from additives, metal working fluids and anti-corrosion packaging materials that are based on environmentally friendly raw materials.

Specifically the company has been working with Cortec Corporation of St Paul, Minnesota, USA, a global manufacturer of biodegradable and environmentally friendly corrosion protection solutions. Cortec Corporation is ISO-14001 certified.

Repair or replacement of corroded metal products represents a multi-billion pound cost to industry and society. Manufacturing businesses continue to strive to reduce product complaints in line with total quality aspirations.

As concerned members of society, we seek low environmental impact yet cost effective ways to protect high value engineered metal products from corrosion so that they arrive in perfect condition to the customer.

Should these engineered metal products (EMPs) arrive at the customer in a corroded condition they will be returned or reworked at the suppliers cost. The scrapping or reworking of the EMP will then have a further environmental impact.

So it is better to get it right the first time and choose a total corrosion protection system that works.

Once you have a corrosion protection system of oils, lubricants, coatings and packaging in place it may be time to start thinking about biodegradable products. We provide a practical explanation of 'biodegradable packaging' and present product systems that have successfully harnessed environmentally friendlier technologies.

Inhibiting corrosion

Corrosion is still the most costly defect automatically built into EMPs when they come into contact with the ambient environment. We can attempt to find an engineering solution by choosing more inert metals such as stainless steel or titanium but even if the more corrosion resistant EMPs (eg chrome plated) arrive in good condition they invariably corrode over time during use.

From the manufacturing supplier's perspective once the engineering specification for the EMP is fulfilled, it is of paramount importance that the EMP should arrive at the customer in pristine condition.

In the case of complex equipment dispatched to the customer location in parts, for example, turbines, it is also important that components remain in good condition until, throughout and after assembly which can span many months.

Corrosion can be stopped by placing an oxygen and water barrier between the EMP and the environment, historically achieved by coating the EMP in oil. On arrival the EMP must be cleaned before use creating an oil contaminated solution and adding process and disposal costs to the customer's operation.

A more elegant route to create an oxygen and water barrier on an EMP is to make a molecular barrier using mixtures of organic corrosion inhibitors specifically designed for multi-metal cathodic and anodic corrosion protection.

The organic molecules are thermodynamically attracted to metals and as long as they are present in a supply reservoir close to the EMP they will form a protective barrier for prolonged periods and in hostile ambient conditions.

The key to cost effective commercial application of organic corrosion inhibitors is the number of ways of getting them to the surface of the EMP under all the conditions that the EMP experiences.

Thus, the basic requirement of the organic molecules is that they should move from the supply reservoir to the EMP under ambient conditions as dissimilar as cold Northern hemisphere winters to equatorial mid-summer days, especially relevant for global shipments.

The diffusion from supply reservoir to EMP is governed by Fick's Law of Diffusion which drives the molecules from the reservoir to the metal surface. The organic molecules that diffuse from a solid or liquid supply reservoir through the air towards a metal surface are called Vapour Corrosion Inhibitors or VpCIs.

No one VpCI will match all requirements of industry and it is the combinations of different VpCIs with different supply reservoirs that are important to tailor a commercially acceptable and cost effective solution.

Health and safety

All classes of corrosion inhibitors are not necessarily friendly to the user. For example nitrites are contact corrosion inhibitors that can decompose forming nitrosamines in the presence of secondary amines which are carcinogenic.

Vapour Corrosion Inhibitors from Cortec Corporation do not contain nitrites or heavy metals and can be handled using normal good working practices.

Supply reservoirs

VpCI molecules are available in a variety of supply reservoirs that when combined provide a bespoke packaging solution to the problem of corrosion of EMPs.

Supply Reservoir - Typical Application:

Bulk VpCIs (powder and tablet) - Vapour phase coating (direct dusting).

Oil based liquids - Flexible, self-healing coatings.

Solvent based liquids - Durable, scratch resistant coatings.

Water based liquids - Environmentally and disposal friendly fluids and coatings.

Paper (sheets and corrugated assemblies) - Puncture resistance, physical separation and basic mechanical protection.

Plastic (stretch film, bubble film and bags) - Higher level protection, ease of use.

Foam (sheets and pieces) - Highest level protection, low weight, high capacity.

A large selection of supply reservoirs means that VpCIs are available to protect internal (eg engines) or external metal surfaces and under a variety of ambient conditions. The VpCI packaging solution encapsulates the EMP and there is no need to create an expensive hermetically sealed package.

Quality and the environment

Since the VpCI molecular barrier is invisible it is essential to work with a reliable partner for packaging solutions. A reliable partner will provide a bespoke VpCI packaging solution using materials of appropriate quality (fit for use) and important on-site application information, all at an acceptable price.

The manufacturer of the VpCI packaging must have total control over the manufacturing processes and ensure the necessary amount of VpCI is transferred to the supply reservoir during the manufacturing process.

Cortec Corporation's R&D programmes have resulted in significant investment in bespoke paper and plastic processing technologies to ensure product effectiveness and consistent quality.

Since by their nature VpCIs will evaporate at elevated temperatures used to incorporate them into a plastic supply reservoir, not every manufacturing process will produce acceptable VpCI products. The manufacturer should therefore have in place bespoke manufacturing equipment and processes in addition to ISO-9001 certification.

If the manufacturer is a serious player on environmental issues then ISO-14001 accreditation will have been achieved.

Environmental considerations

Biodegradation is an emotive subject and catches the imagination of the customer and in particular the end-consumer. The ability to throw away packaging for it to fertilise the earth for future generations is captivating but currently difficult to achieve without compromising on packaging performance and price.

And of all the opportunities to save the environment, is it more acceptable to recycle or down cycle plastic rather than to encourage it to degrade?

Any solution requires the customer to sort and separate waste into different streams which is easy to say but difficult to implement in some industrial societies.

The technical evaluations of the best environmental route must involve a cradle-to-grave analysis of the waste stream which can be very complicated. The types of decomposition are described below:

Type of Decomposition - Description

Degradation - An irreversible decrease of polymer molecular weight causing a change in mechanical properties.

Disintegration - Falling apart into very small fragments caused by degradation.

Biodegradable - Degradation caused by naturally occurring micro-organisms eg bacteria, fungi, algae.

Compostable - Degradation by biological processes to yield CO2, water, inorganic compounds and biomass at a rate consistent with other compostable materials leaving no visible distinguishable or toxic residue.

Three examples will demonstrate the importance of these categories. Firstly consider a standard HDPE physically mixed with starch (polysaccharides).

This product is engineered to have the same mechanical properties as HDPE but when attacked by microbes the starch biodegrades and the HDPE degrades and eventually disintegrates, but the HDPE/starch blend is not compostable. In fact the HDPE/starch blend is compostable to the amount of starch added.

Since the introduction of PE/starch blends to solve the 'white trash' problem endemic in eastern countries (especially India and China) prices for application in the European market are now very acceptable and there is no blocking technical or commercial reason for the use of these products.

Secondly consider a synthetic aliphatic polyester plastic film made from renewable plant resources which has comparable or improved performance over LLDPE. The aliphatic polyester is biodegradable and compostable.

Thirdly consider cellophane, a naturally occurring polysaccharide polymer that is not generally used in industrial packaging applications because of its intrinsic poor mechanical properties. Cellophane is biodegradable and compostable.

Of course this discussion presumes that the additives and pigments used to make the plastic products are compatible with the degradation mechanism of the polymer.

Surely, any of the above is preferred to dumping plastic into landfill and there is an ongoing wealth of research, product development and information on this subject by many companies and academic institutions.

However complicated the analysis we come back to the point that the market will fulfil the needs of the customer. Companies that wish to show the world they are concerned about the environment will choose an environmentally acceptable solution.

For the protection of EMPs against corrosion, environmentally preferred VpCI plastic packaging solutions are available from Cortec Corporation based on 100% biodegradable and compostable polymers.

Aerosols

In the 1950s aerosol technology brought new and innovative ways to deliver rust preventatives and was a success in spite of the potential blanket delivery, strong odour and environmental hazards.

The innovation in propellant technologies for aerosols has continued and today compressed air is the most environmentally acceptable medium for delivering VpCI liquids to the EMP.

It is important to consider all components of the delivery system and apart from a recyclable can it is important to use water based VpCI products that are also biodegradable such as Cortec's EcoAir product range.

Water based systems

Using water based VpCIs in place of oil is a sensible technical and commercially preferred solution to corrosion prevention for EMPs. The VpCI barrier replaces the oil and water is used as the carrier in place of solvent as it is more environmentally acceptable.

Although universal substitution in all applications is not possible, all industries using oil and synthetic solvent based VpCI products should consider changing to water based VpCIs.

An additional benefit of water based VpCIs coming into contact with water or seawater is that the molecules are biodegradable and harmless to the environment. A study of VpCI showed that the molecule is biodegradable within 28 days, is unlikely to bio accumulate and is not an acute toxicant to aquatic life.

Biodegradable oils and greases

As the issues surrounding biodegradability are more thoroughly studied, the need to use natural renewable plant resources becomes important. EcoLine products from Cortec Corporation are based on renewable resource soybean derivative, soybean methyl esters, and rape seed oils.

These VpCI oils with low environmental impact technology are easier to dispose of than traditional mineral oils. Also the soy-bean technology provides excellent lubrication and like other commercial plant based oils they are a winning substitute for older technologies.

Environmentally acceptable

Engineered Metal Products can be protected from the harmful effects of corrosion at an acceptable cost by implementing a total solution (VpCI - liquids, papers, foams and plastic films) based on a technical evaluation of the packaging needs.

The bespoke VpCI solution can be adapted to take into account the environmental impact by choosing water based media, air-propelled aerosols and environmentally friendly biodegradable oils, papers and plastics.

Dr Steven Cartlidge is a chemist, and managing director of Redditch-based technical distributor Lake Chemicals and Minerals. Brian Coles is metallurgist with the same company.