Tag Archive for: Corrosion protection

ESEF Maakindustrie

30 Aug – 02 Sep 2022 Utrecht, The Netherlands

We look forward to get in contact with you again at the ESEF Maakindustrie!

During this event, we would like to introduce our MM31, the innovation in the field of metal cleaning. It cleans, degreases, offers corrosion protection and paint adhesion in 1 step. It is an efficient and safe alternative to solvents.

Replace degreasing solvents with MM31:
✔ Safer for people and the environment
✔ Water-based degreasing with protection against flash rust
✔ Excellent degreasing power
✔ Corrosion Protection
✔ Improved paint adhesion

Are you ready to draw a line against the use of solvents with us?

Please get your free ticket here (click on the picture below):

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Replace solvents (Solvents) with MM31

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.

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Achieve excellent corrosion resistance and paint adhesion for any metal in just 1 step!

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.

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Seminar: Innovation in coating processes for heavy duty steel constructions

AD Chemicals will highlight the latest developments in coating and pretreatment at the Surface Campus, 14-11-2018, Brabanthallen Den Bosch, the Netherlands. See the program below:

Register for this seminar for free at: https://surfacecampus.nl/2018/10/10/innovatie-in-coatingproces-voor-opdrachtgevers-chemicalien-en-lakleveranciers/

 

Locatie Conferentieruimte A
Thema Voorbehandeling
Zaalvoorzitter Roland van Meer
13.30 – 14.00 uur Low temperature zinc phosphate: An innovative concept reduces process costs and saves money (Engels)
(meer informatie)
dr. Ulrich Hönig
(Kluthe Benelux)
14.00 – 15.00 uur Combipresentatie: (meer informatie)
Hollandia: Innovatie binnen de conservering van staalconstructies
Wim van ‘t Hof en Nardo Hoogendijk
(Hollandia Infra)
Game changer voor oppervlaktepreparatie voorafgaand aan coatingproces
ing. Roland van Meer
(AD Chemicals)
Blik op innovatie staalconservering vanuit de lakleverancier
Anita Snoeren
(Powder Supply)

Comprehensive congress programme

SURFACE Campus will offer around 75 different lectures in hall 4. Let the stories inspire you. Take master classes to put theory into practice. And present your issues to experts during one of the consultation moments. The congress hall is where you’ll be the first to hear about the latest developments. So be there, if you want to stay up-to-date.

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Alternative Corrosion Protection Pre-treatments for Aluminium Alloys

Aluminium alloys are extensively used in space programs for both structural and non-structural applications. As well known, the corrosion resistance of these alloys is quite limited and anticorrosion treatment is needed.

The most used treatment currently used for improving the corrosion resistance of aluminium alloys are usually chromate (CrVI-based) conversion coatings (CCC). Due to the high environmental impact of these compounds, the REACH Regulation of the European Union decided to limit/restrict the use of hexavalent chromium. A sunset date of mid-2017 has been already set.

For the time being many chromate-free alternative products are available but they have found to be significantly inferior in terms of corrosion protection performances with respect to the chromate options. In this regard there is a great need to develop high performance hexavalent chromium-free anti-corrosion coatings with low environmental impact and conformity with the EU regulations.

The European Space Agency (ESA) is currently involved in a TRP contract with Instituto de Soldadura e Qualidade (ISQ) that is currently on-going. The objective of this study is to evaluate the anticorrosion behaviour of the different alternative pre-treatments applied to the most used aluminium. The outcome of this activity will be the identification and the optimization of the most promising anticorrosion pre-treatment.

Several commercial Cr(VI) free processes were applied onto aluminium alloys (2024-T3 and 2024-T81) used in the construction of ESA spacecraft, in order to investigate their anticorrosive properties compared with Alodine 1200, a widely used conventional CCC. One of these commercial processes (PreCoat A32) presented good anticorrosion performance, even better than Alodine 1200 and these results are presented in this paper.

Salt spray resistance is included in the testing program as well as metallurgical coating evaluation that include microscopy (SEM) observations before and after testing and electrochemical impedance spectroscopy (EIS), in order to evaluate surface and microstructural modifications due to degradation mechanisms. Further studies must be performed with the this promising alternative, modifying application parameters, in order to achieve improved corrosion protection efficiency.

Key Words: Aluminium alloy, Conversion coating, Anti-corrosion coatings, SEM, EIS

Source: Whitepaper Springer.com,Journal of Coatings Technology and Research, pp 1–14, Alternative corrosion protection pretreatments for aluminum alloys

Interested in PreCoat A32 passivation or the full whitepaper? Contact chemicals@adinternationalbv.com

precoat_a32_bare_corrosion_protection

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THE CHROME-FREE PRETREATMENT

It is well known now that some well described Qualicoat pretreatment procedures are very critical in obtaining good adhesion of powder coating and sufficient corrosion protection.

Proper etching/pickling to remove the most sensitive Aluminium top layer and sufficient rinsing are two of these important pretreatment steps.

Even though job coaters are following Qualicoat procedures most of the time when adhesion or corrosion issues occur the failure can be found in the pretreatment steps and not in the conversion bath or in the powder coating cycle. It seems that the newly developed Cr (VI) free conversion coatings are less forgiving than former chromate conversion coatings.

AD Chemicals and her customers are working closely together to determine the critical pretreatment steps. Pickling, racking and rinsing procedures can be optimized to guarantee the best performance possible with Cr(VI) free conversion coatings.

In this presentation we will discuss some factors

that might influence the quality of your powder coated aluminium.

Introduction

Each powder coating line has it´s own challenges. You have to be aware of the best processes prior to the painting of Aluminium objects. The starting point must be that a

The ultimate goal is to work with Chromium (VI) free pretreatments while maintaining the quality properties between Aluminium and paints. Also to meet the required specifications of Qualicoat.

First let’s focus on the variables of the pretreatment line and the quality of the Aluminium.

Concerning the quality of the Aluminium, an assessment of the quality is essential. However, jobcoaters have no influence on this question. They are depending of the Aluminium quality which they received from their sources. The only thing the jobcoater can do is to ask for a quality certificate of the Aluminium or a certificate of analysis of the formation of the Aluminium. Only the structure of the pretreatment line and the chemicals is in control of the jobcoater.

For example: Structure of a Pretreatment line(spraying), chromium (VI) free application

  1. Degreasing /Acid pickling >1.0 g/m2
  2. Rinse
  3. Rinse
  4. D.I. Rinse
  5. Chromium (VI) free pretreatment

 

Stage 1: Pretreatment tunnel, Pickling phase

Due to the increasing demands from Qualicoat (for example, sea-side > 2 g/m2), the pickling rate (etching-rate) has to be increased in the pickling (etching) phase. This means that you have to increase the aggresivity of the chemicals in the pickling phase. Important note is that when there is a stop in the line speed aluminium profile will be exposed by wet pickling solution and aggressive acid vapor. This “pollution” can dehydrate on the Aluminium surface. It is highly recommended to use a water curtain in case of an outage, as this will prevent acid drying effects. Experience has shown that dried-acid residues on the aluminum surface will not be removed totally in the rinsing phases. Residues can be a possible influence for the chromium (VI) free pretreatment. The formulation of the acid pickling is also a factor to prevent acid drying problems. AD Chemicals monitors it’s formulation at costumers to prevent undesirable effects. Other important items to prevent undesirable effects are good maintenance of the spraying nozzles, temperature, spraying pressure, contact time and the build up of the Aluminium content in the pickling solution.

Stage 2 and 3: Pretreatment tunnel, 2x normal rinse (tapwater)

The both rinsing phases are very important. The difficulty in these phases is that the rinsing water reaches all shapes and surfaces. Especially the seams of insulated profiles have to be rinsed well. In the seams acid residues stick and the rinse water flows over the pollution, this effect results in a minimum mixture with rinse water. The temperature of the rinse water is recommended to 18- 20oC, lower temperatures of the rinse water result in more viscous water and the rinsing effect will be less. The quality of the rinse water will be controlled by pH and conductivity.

Stage 4: Pretreatment tunnel, D.I. rinse water

The best rinsing quality will be if the conductivity is < 30µS and with a pH between 4,5 and 6,0.

At these parameters the risk of contaminations on top of the aluminium surface is minimized. This phase is highly important because any pollution can influence the last phase, the chromium (VI) free pretreatment phase.

 

Stage 5: Pretreatment tunnel, Chromium (VI) free pretreatment

The chromium (VI) free preatreatments of AD Chemicals are based on a precipitation reaction, where the conversion layer will be made. This layer is a cross linking layer for organic coatings. The thickness of this layer is very important. A layer that is too thick, results to bad adhesion and will be humidity sensitive.

A layer that is too thin, influences the adhesion at the bending tests. By guaranteeing the parameters like conductivity, pH and concentration, the chromium (VI) free layer can be assured. There are several types of chromium (VI) free pretreatments available for Aluminium. The most common types are based on the reactive groups titanium/zirconium (marked named by chromium free pretreatments) and chromium (III). All those Chromium (VI) replacements confirm the 1000hours Salt Acid Spray, corrosion resistance test requirements of Qualicoat.

 

One very important question bothers AD Chemicals:

“Is the requirement of 1000 hours corrosion resistance which Qualicoat prescribes enough?”

AD Chemicals doubts this statement of Qualicoat. When you only focus on the 1000 hours corrosion resistance, that has been described in the past, Qualicoat is right. However, the corrosion resistance of chromium (VI) based pretreatments fulfills the 2500 hours. This was a fair value for Chromium (VI) based pretreatments on Aluminium. AD Chemicals has investigated their chromium-free systems on the corrosion resistance of 2500 hours and compared it with the traditional chromium(VI) systems.

 

Internal research shows that the chrome free pretreatment of AD Chemicals precoat CR-FREE A-021, that has been approved since 2003, achieved a corrosion resistance of 2500-3000 hours.

 

The following reaction takes place on the surface:

When there is a good etching in the way that all the oxides are removed of the surface and the alloys are complexed then the layer is ready for the interaction with our PRECOAT CR-FREE. So there will be a interface bonding between our precoat and paint.

By proper process optimizations and pursuing the parameters and variables with fine chemicals, Chromium (VI) free pretreatments are perfect replacements of Chromium(VI) based pretreatments.

precoat chrome free pretreatment qualicoat

 

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