Gulf Construction Online - New topcoat tackles severe conditions

Corrosion

Hempaxane 55000... protects steel structures exposed to harmful environmental conditions.

New topcoat tackles severe conditions

01 June 2003

Hempel has recently launched a new high-quality topcoat which is said to be ideally suited for steel structures exposed to severely corrosive atmospheric environments.

Known as Hempaxane 55000, the unique product is based on both epoxy- and polysiloxane binder chemistry, thus combining the excellent anticorrosive properties of epoxies with very long colour- and gloss retention from the polysiloxane binder, according to a spokesman for the international paint manufacturer.

"Most of its product features clearly outperform those of polyurethane topcoats," he says. "Furthermore, the product has an environmentally-friendly profile, which is clearly on the forefront of all foreseeable restrictions concerning solvent emission."

Hempaxane 55000 has undergone thorough testing at every stage of development. This has involved in-house testing and field trials on a wide variety of different structures. Furthermore, the product has obtained certification by some of the world's most recognised coating institutes. It has already passed pre-qualification for Norsok M501 - rev4 standard using only a zinc-rich primer as a preceding coat, he points out. Other tests include mechanical strength, abrasion resistance and colour and gloss retention tests, all according to recognised standards.

"Hempaxane 55000 has proven superior to other topcoat products currently used in the market in terms of colour and gloss retention, impact, abrasion resistance and anticorrosive barrier properties - helping to ensure longer durability of the structures protected with this coating," the spokesman claims.

Hempaxane 55000 is designed to protect steel structures from the harmful effects of weather, environment and operating conditions, whether this is offshore, onshore or inland. Some of the more typical constructions include offshore installations, petrochemical plants, tank farms, wind turbines and bridges - all structures where a very long durability is expected and where maintenance can be difficult and expensive due to limited access.

It forms a hard coating within only a few hours, making the product ideal for use in online production facilities or other situations where fast drying means faster throughput and increased production flow, according to the company.

"Hempaxane 55000 provides much better corrosion protection than conventional topcoats such as polyurethanes," the spokesman continues. "This is possible because it forms an exceptionally effective barrier to the passage of water and also a very hard, impact- and abrasion-resistant coating to protect against mechanical damages.

"Furthermore, it is extremely resistant to ultraviolet (UV) light from the sun, meaning that the coating maintains its gloss and colour for much longer than other topcoats, such as acrylics, alkyds and polyurethanes. Structures painted with Hempaxane 55000 will therefore maintain their aesthetics for many years to come.

"Due to the combination of colour and gloss stability with corrosion protection properties, Hempaxane 55000 can substitute both an epoxy coat and polyurethane coat and thereby, in certain cases, reduce the number of coats in a coating system."

As an example, a typical coating system in a C3-C4 environment (according to ISO 12944), would include a zinc-rich primer, followed by both an epoxy intermediate coat and a polyurethane topcoat. The last two coats can be substituted with just one coat of Hempaxane 55000, he explains.

With the increased attention on the environment, most countries are expected to impose further restrictions related to solvent emission and content of hazardous material in coatings over the coming years.

Hempaxane 55000 has a solids content as high as 85 per cent and a VOC (volatile organic compound) level as low as 160 g/litre. This means a significant decrease in solvent emission compared to alkyds, polyurethanes and most epoxies, the spokesman says.

"It is also totally free of isocyanates," he says. "At present, isocyanates are only prohibited in coatings in a few countries, but their health and safety aspects are an issue of continuous consideration. It is expected that more countries in the years to come will enforce the use of alternatives to isocyanate containing topcoats."

Hempaxane 55000 is available from most Hempel companies around the world.

Earlier this year, Hempel also introduced a new high-build epoxy coating reinforced with lamellar glass flakes, to meet the protection requirements from some of the most extreme corrosive environments.

Known as Hempadur Multi-strength GF 35870, the product combines all the features of a high-build epoxy coating with the properties of glass flakes which makes it extremely resistant to wear and tear, chemicals and corrosion, according to the spokesman.

"It is designed to withstand the extreme conditions prevailing in the offshore industry, on areas such as splash zones, helidecks and working decks which are exposed to severe abrasion in a highly corrosive environment," he says. "The product can also be used on water treatment facilities, sheet piling, pulp and paper mills and water dams, which also require proper protection against abrasion and corrosion.

"The coating meets the most stringent solvent emission regulations in the world. With a VOC level as low as 177 g/litre and a volume solids content as high as 87 per cent, the product emits far fewer solvents into the air than most other epoxy products.''

Its high volume solids content means Hempadur Multi-strength GF 35870 can be applied in dry film thicknesses as high as 350 to 500 micron, even on vertical surfaces. Furthermore, the product is self-priming and can therefore provide structures with extremely good corrosion protection in just a one-coat system, he says.

Another product feature of Hempadur Multi-strength GF 35870 is its fast drying properties which means structures can be exposed to water only few hours after the product is applied.