Waterbased Direct-to-Metal Coating

Posted : 17 May 2018

Unprotected steel in the atmosphere, in water and in soil is subjected to corrosion that can lead to damage. Therefore, to avoid corrosion damage, steel structures are normally protected to withstand the corrosion stresses to which they will be subjected during the service life required of the structure. Solvent based metal coating such as alkyd, acrylic, epoxy, are common materials chosen to protect steel from rust. However, regulation and consumer-driven interest in lowering VOC and HAPS have pushed the need to replace solvent based coatings with waterbased Direct-to-metal alternatives.

Direct-to-metal (DTM) coatings can offer huge gains in production efficiency and cost savings yet need to meet tough performance requirements. The polymer chains in the acrylic latex polymers are already at a very high molecular weight and do not need to undergo the cross-linking reaction to develop its properties. Therefore, they are one-component and easy to use –no more mixing and no pot life issues to worry about.

The secret for making waterborne coatings with the ability to withstand tough environments was to be found in the nature of the resin – the major component in the coating. Better solvent resistance, corrosion resistance and weathering with outdoor exposure means the coating will last a long time. Its durability and lower usage of TiO2 is a strong value proposition for offering formulated cost savings tocustomers. The more efficient distribution of TiO2 in the film means less of the pigment is needed to obtain good hiding, and the low-VOC capability cuts down on the need for other film-forming agents, all of which could lead to lower manufacturing costs.

Formulating waterborne coatings that are intended to protect metal comes with a unique set of challenges. A very good dispersion of pigments is necessary to avoid agglomeration and resulting film defects that allow water penetration into the film. Dispersant choice that is compatible with major processes by the process by maid service the binder is critical for corrosion resistance. Additives such as defoamers, wetting agents and thickeners are necessary components of any coating formulation. However, they can also negatively impact corrosion and water resistance properties. One additive that must be included in all waterborne Direct-to-metal coatings is a flash rust inhibitor to prevent flash rust of the metal during the drying process. Simple substances such as sodium nitrite cab be used, but often commercially available flash rust inhibitors will contain additional ingredients that improve effectiveness and also provide an improvement in corrosion resistance.

Recent Develompments

PT. Aristek Highpolymer as a leading company in the development of a waterbased acrylic latex polymers for Direct-to-metal applications. Some of our product include:
GreenPol™ 1115 – This product offers excellent chemical resistance and very high flexibility with excellent adhesion to galvanised & non-ferrous metals. It is designed for two- component systems (2K) for stoving applications in coil coatings.

GreenPol™ 1125 – This product is a soap free emulsion, medium to hard polymer, with good adhesion on any metallic substrate. It can be formulated as a primer and top coat in one-component systems (1K). Designed for air drying applications of protective coatings and suitable for clear coat applications.

GreenPol™ 1276 IM – This product is a hard polymer with good adhesion on any metallic substrate.  It can be used as a primer and top coat in one component system (1K) for air drying applications.

GreenPol™ 1276 HA – This product is a self-crosslink polymer with good anti-corrosion properties,  outstanding alkali and chemical resistance and excellent adhesion to galvanised & non-ferrous metals. It is suitable for light duty metal coatings, as a single layer for Direct to Metal (DTM), and in one-component system (1K) with air drying applications.

Our products stand up to solvents, chemicals, and adverse high temperature and humidity weather conditions.  With these products, the challenge of lowering VOCs is also addressed.