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MM31 can replace solvent-based processes for cleaning and degreasing metals 1-on-1.

Nowadays the use of solvent-based cleaners (so-called solvents) such as thinner, xylene and heptane, is under the microscope. Just think of the danger that the use of such substances entails in terms of working conditions and fire safety. Reducing environmentally harmful emissions and VOC (Volatile Organic Compounds) housekeeping are also frequently discussed topics. This is independent of the extra focus on such substances brought by government agencies and inspection bodies.

The cleaning and coating of metal in practice

In practice, we see that solvents are used less and less in coating systems and that when such coating systems are used, this is done with the proper attention to personal protective equipment (PPE). However, when looking at the metal cleaning process prior to this coating process, many organisations still use solvents, with all the associated risks for people and the environment. And whereas the correct PPE is often used when it comes to the coating process, it is often forgotten in these types of processes. A frequently heard statement is “we have been doing it like this for years…never even thought about it”.

Working with solvents, how effective is it?

Solvents are known in the market as powerful metal degreasers. However, how effective are these products in practice? In general, it can be said that such products are applied using a cloth, in which case the cloth is maybe used several times in most instances. However, by rubbing with the cloth and evaporating the solvent, the grease layer is smeared rather than removed, with all the consequences that entails in terms of cleaning the metal. Because the metal has not been properly cleaned, there is a risk of corrosion and paint detaching on high-quality metal structures with extensive paint systems (even if a thorough mechanical pre-treatment such as blasting is applied after cleaning). This includes unexpected places, such as flat parts. This can be for various reasons, such as not working according to specifications and applying thin layer thicknesses. Much more often than not, however, the cause lies in incorrect surface treatment when it comes to cleaning. The prepared surface is still dirty or even greasy after cleaning with solvents. The solution that first springs to mind doesn’t usually involve correcting the cleaning process, or people simply don’t want to see this as a problem. In such situations, a simple test provides a definite answer, i.e. the water break test.

The water break test: a view of correct cleaning of metal at a glance

The water break test is a simple, quick and usually non-destructive test (can cause flash rusting on steel) to test the presence of water-repellent films. The test is applied to freshly cleaned metals such as steel and other metals that are hydrophilic in a completely clean state. In this case it often shows contamination of the substrate because the water film is broken. This test quickly shows whether a cleaning agent has done its job, for solvent-cleaned surfaces this is often only to a limited extent. “Isn’t there any other way?”, you may think. The answer is a resounding “yes”. AD Chemicals introduces a replacement product for solvent-based cleaning under the brand name MM31.

MM31 can replace the current solvent-based process step 1-on-1. In addition, the product is free of ADR hazard labels and can be used on multiple types of metal. This allows it to be used safely for people and the environment. Let’s take a look at the difference by using the water break test. Attached picture 1: shows the difference where the result “passed” was treated with the solvent replacer and “not passed” was treated with a solvent.

Several companies in the European market are now already opting for this sustainable, environmentally friendly and improved health-and-safety alternative. The product is already finding its way to leading trailer manufacturers and machine builders, among others. See the accompanying photo of the water break test in a field application. Judge for yourself which part has been treated with MM31.

Extra added value: rust protection, corrosion protection and paint adhesion

In the search for an alternative to cleaning with solvents, AD Chemicals has been able to upgrade the cleaning process. This is done by adding added value to the metal.

In addition to a clean, well-degreased surface, MM31 also creates a so-called conversion layer on the substrate. This conversion layer offers the following benefits:

  • Passive technique: protection of the substrate without coating and protection against flash rust in conditioned storage for up to a few days
  • Improved paint adhesion and corrosion protection

Watch the video with the application process here:

Insert video

See Figure 3 for salt spray test results and Figure 4 for flash rust protection on steel.

Figure 4: Flash rust protection

 

Companies that convert the cleaning process to MM31 achieve clear advantages in terms of both environmental and labour technology, as well as quality.

Product demonstration on location with customers

Currently, AD Chemicals offers free on-site product demonstrations for interested parties. Contact our team via chemicals@adinternationalbv.com for the possibilities and to schedule a demo.

The industry is currently looking for alternative (wet) paint systems that achieve the same results in terms of corrosion protection and paint adhesion as chromate/Chrome-VI-based paint. MM31, a new development in chemical technology from AD Chemicals, could be the answer. The product is easy to apply in just 1 step in the mechanical pre-treatment and significantly improves corrosion resistance and paint adhesion.

Why pre-treatment on steel

Organic coatings are applied to steel to prevent or at least delay damage caused by corrosion. This is often based on a combination of the following mechanisms:

  • protection against (aggressive) ions
  • barrier to moisture and oxygen
  • slow anodic dissolution reaction with pigments (chromate, phosphate, etc.)
  • cathodic corrosion protection (zinc dust).

To obtain good durable adhesion under corrosive conditions, the steel must be properly prepared before applying a coating. The purpose of the pre-treatment is to get a consistent surface quality in terms of:

  • cleanliness: dirt, oil, grease, paint residues, rust, mill scale
  • roughness: can contribute to the adhesion and appearance of the paint layer
  • chemistry: metallic, oxidised or with a chemical conversion layer

Common pre-treatment methods

The most common pre-treatment methods for steel listed in the table below.

Method Pre-treatment Purpose Disadvantages
Water-based degreasing Remove: oil/grease/dirt Not practical outside of paint shop, rinsing necessary, waste
Stain Remove: mill scale, rust Not practical outside of paint shop, rinsing necessary, waste
Solvent-based degreasing Remove: oil/grease/dirt •       Safety, Environment

•       Dirt not completely gone

•       Fire hazard

Mechanical (including blasting/sanding) •       Removal: mill scale, rust

•       Create uniform roughness

•       Remove oil/fat first

•       Remove dust afterwards necessary

Chemical conversion layers More passive layer than metal: often with additional adhesion and corrosion properties

 

Each pre-treatment method has its advantages and disadvantages. In general it can be said that today the following 5 points are the main challenge for the preservation of the steel industry:

  1. Improve working conditions;
    • No Cr6 + in (conversion) coatings
    • No exposure to solvents due to OPS.
  2. Reduce environmentally harmful emissions;
    • Replacing solvent cleaners (thinner, xylene, heptane)
    • 0% VOC emission
  3. Extend the time between mechanical treatment and coating;
    • Prevention of flash rust in temporary conditioned storage
  4. Waste reduction
    • g. replacing pre-treatment bath with a no-rinse treatment
  5. Cleanliness of the surface after blasting;
    • Fat and oil still blasted into the surface. Dust present as a result of the blasting.

New pre-treatment method: combination of blasting and chemistry

Generally, it can be said that in the wet paint industry, a mechanical pre-treatment by way of blasting or sanding is the most commonly used method. What if the aforementioned pre-treatment methods can be combined?

This is the power offered by a new development in surface treatment from AD Chemicals. Known under the brand name MM31, its product combines blasting and chemical pre-treatment. If a chemical surface treatment is carried out, the procedure includes degreasing, staining and applying a conversion coating. The conversion coating provides corrosion protection and paint adhesion. The degreasing and staining step is similar to the degreasing and blasting method. After blasting, there is no additional added value to the metal, as is the case with a chemical pre-treatment by applying a conversion coating. This means that this mechanical procedure basically only ensures good paint adhesion and does not impart additional added corrosion-resistant properties to the substrate. However, by applying a conversion coating after blasting, the two worlds come together, improving the quality of the coated product in terms of adhesion, as well as corrosion resistance.

Corrosion resistance and paint adhesion improve significantly in just 1 step!

Risk of corrosion after blasting

Steel structures that are coated after sand or grit blasting run a risk of corrosion despite high-quality systems and careful preparation of the steel surface. Even in unexpected places, like flat parts. This can have various causes. Sometimes layer thicknesses can be too thin, but the cause, more often than not, is in incorrect surface treatment after blasting. The abrasive is dirty or even contains grease. A solvent-based degreaser is often used before or after the blasting process. This ensures that the grease layer is smeared rather than removed, with all the inevitable consequences. This undesirable result can be demonstrated with a water break test. The water break test is a simple, fast and non-destructive test for the presence of hydrophobic films. The test is applied to freshly cleaned metals, such as steel and other metals that are hydrophilic in a completely clean state and in this case often shows contamination of the substrate. The test is described in ASTM F21 and F22 or MIL-DTL-53072.

Conversion coating properties for blasting applications

MM31 is a Chromium-3 containing product that offers a remedy for the aforementioned causes of corrosion. Notably, it removes grease, it ensures better adhesion of the coating system and protects against flash rust and creep corrosion.

In addition to adequate degreasing, a so-called conversion layer is created by using MM31. This conversion layer is a non-organic, water-based coating which is formed on the metal by way of the constituents, the metal itself contributing to the formation of the layer. From a chemical technical point of view, the following happens: Chromium-3 acts as a strong carbide former and bonds with the iron parts. After blasting, a protective crystalline layer with a surface of ‘hook’ forms, which increases the adhesion of the coating. Moreover, these crystals ‘refine’ the dips in the steel surface that arise during blasting, creating a relief with fewer high peaks, resulting in a more even surface.

 

The purpose of a conversion layer is twofold. The layer improves anti-corrosion properties and provides good adhesion for organic coatings. The thickness of a conversion layer is indicated in milligrams of conversion layer or conversion elements per m², because the layer is usually too thin for the measuring range of the common layer thickness gauges. It is therefore a wafer-thin layer (<0.1 μm) that is many times thinner than a regular coating layer, which, for example, has a layer thickness of 60-1000 μm. An important point is that the conversion layer should not be confused with a regular coating layer such as a primer.

The test results speak for themselves:

The product is applied directly after blasting, or following any other type of mechanical pre-treatment, in-line with a misting installation or manually by means of a cloth or a low-pressure nebuliser (plant sprayer) at room temperature. MM31 can be used for treating completely new constructions as well as for maintenance work on location.

MM31 is water-thin and when applied it also easily treats difficult-to-reach corners and edges of a workpiece. The surface turns blue or dark grey when properly operated, similar to the blue glow that is also characteristic of surface treatments such as iron phosphating, and thus immediately detects the imperfections. After drying, any paint system can be applied.

The quality that can be achieved meets the Qualisteelcoat or GSB Steel requirements. The product is free of ADR hazard labels.

Protection against flash rust

Normally, blasted objects should be coated immediately within a few hours after blasting, or the first forms of corrosion will occur. MM31 offers protection against flash rust, so uncoated objects can be stored longer before being coated. In covered storage for up to 2-4 weeks and in many cases up to 48 hours! As a result, a higher efficiency and output can be achieved when it comes to the processes carried out by coating companies. This offers great advantages in situations such as internal transport and delays in applying the coating, and it makes it possible to buffer parts to be coated prior to the coating process.

Solvent replacement

The replacement of solvent cleaners such as thinner, xylene, heptane is an important challenge for the preservation of the steel industry in connection with the risk of fire hazards, working conditions for employees and the 0% VOC emission target. MM31 offers an answer to this and can replace these solvents in the degreasing step in the pre-treatment of metal. The outcome? A better quality, a safer working environment and cost savings can be achieved.

Reinforcement paint systems without chromium (VI)

Another important aspect is that, at present, in many sectors such as agriculture, machine manufacturing, infrastructure, tank construction and the transport sector, alternatives to Chromium-6-containing primers are sought after for good corrosion protection on products. The harmful effects of such systems for human beings and the environment are now widely known. MM31 makes it possible to improve the final quality on a variety of chromium (VI)-free coating systems. The product can therefore make a valuable contribution to achieving high-quality coating systems of a comparable quality to Chromium-6. This fulfils a long-expected market need. AD Chemicals is therefore happy to enter into talks with potential paint suppliers and coating companies about creating more synergy between the pre-treatment and the paint system.

Comparison test?

Are you curious about what this technology can mean for your process and how it relates to your current situation? Contact us via chemicals@adinternationalbv.com for more information.

One of the most important factors influencing paint adhesion and corrosion resistance is surface preparation. To ensure optimum performance and long-term environmental resistance, metal substrates must be free of organic and inorganic contaminants. To prepare a surface one can basically choose between 2 options, blasting or chemical pretreatment.

 

  1. Mechanical/Blasting – Abrasive particles (sand, grit or metal oxides) are projected against the surface with a stream of air. The character or quality of the treatment is affected by duration of the blast; shape and size of the blasting media; particle velocity; and the hardness, porosity and other substrate properties. A metal surface treatment of blasting ensures a uniformly cleaned surface and good paint adhesion but lacks corrosion resistance on the substrate.

 

  1. Chemical processes, on the other hand, utilize organic and inorganic chemicals to achieve two reactions: • Dissolve, suspend or eliminate soils and surface contaminants. • Convert metal surfaces from the essentially free metallic state into metallic compounds.New option: Combining the worlds of blasting and chemical processingCurrently, AD Chemicals, a subdivision of the Dutch AD, International launches a revolutionary new product on the global grit/sand blasting market. This product is called PreCoat F31/20 suitable for the treatment of substrate steel and PreCoat Z31/20 for the substrates aluminum and galvanized steel. PreCoat is a chemical treatment applied directly after grit/sand blasting or metallization (also referred to as metal spraying). This product portfolio is the result of an R&D trajectory of more than 8 years. PreCoat F31/20 and Z31/20 significantly improve the quality of sandblasted or metallized products.

It has two main benefits; by applying the product directly after grit/sand blasting, a conversion layer is created that substantially improves the adhesion of the painting system (suitable for wet painting and powder coating) and significantly enhances the corrosion-protection resistance properties of the paint system as a whole. The application procedure of PreCoat is very easy and can be easily integrated in every business processes.

The innovative aspect of these products is that it combines the worlds of grit/sand blasting and chemical pre-treatment.

PreCoat F31/20 and Z31/20 are based on PreCoat Z31, a product that won the Dutch Innovation Award for surface treatment, ION Borghardt Award 2016.

AD Chemicals is introducing this product on the worldwide market. The first user responses are very promising. A large blasting company in the Netherlands stated: “With this product I am able to improve to overall quality of my products and therefore offer my customers more value. It is a tool to distinguish myself in a competitive market place”

Besides that the responses from our agents in Spain and the UK are very promising.

As products are better protected against corrosion, the product lifetime increases and thereby lowers the ecological footprint. See below the pictures after 500 hours salt spray testing where the difference is demonstrated between the regular automated grit blasting process and the grit blasting process with PreCoat treatment.

precoat blasting powdercoating chemical pretreatment test results

Want to know more about this innovation? E-mail to chemicals@adinternatonalbv.com