Cooler, borate-free cleaning for mixed-metal lines

Nobody gives a prize to the cleaning stage. Yet every bond, conversion coating and coat of paint on a component is only as good as the surface it lands on, and that surface is prepared in a tank or spray cabinet that the plant must heat, treat and eventually discharge. BONDERITE C-AK 5831 ECO, Henkel’s borate-free, mildly alkaline cleaner for metal parts, is an attempt to ease all three of those burdens at once.

What the cleaner is built to do

Baschir Harb, Technical Manager Light Metal Pretreatment for Henkel’s Surface Treatment Cleaners and Lubricants business, describes the product’s origin story, saying, “BONDERITE C-AK 5831 ECO was originally developed as a borate-free, mildly alkaline aluminium cleaner with little to no etching effect."

"When combined with a suitable surfactant additive, the product removes process-related contaminants such as greases, oils, and metal chips, as well as other residues from upstream machining operations. A particular focus lies on the removal of welding smut from aluminium surfaces.”

The surfactant clause here, matters. The cleaner itself is a builder, made from alkali, phosphates and phosphonates, and it relies on a partner from Henkel’s BONDERITE C-AD range to do the soil work. Henkel pairs C-AD 1400 (immersion) and C-AD 5003 (spray) with the conventional 50°C to 60°C window. It pairs C-AD 20202 (immersion) and C-AD RT 1020 S (spray) with a cooler 30°C to 40°C window. The company says the combination lifts weld scale without attacking the aluminium beneath, which is the trade-off that makes the metal awkward to clean.

Where it sits on the line

The product is not confined to the pretreatment tunnel, however. Harb explains how far its flexibility stretches. “Within the production process, BONDERITE C-AK 5831 ECO stands out for its high efficiency as a builder,” he says. “The product can be used both as a pre-wash and intermediate wash in manufacturing processes involving mechanical machining, and as a cleaner in pretreatment lines. Its high process flexibility allows for use across a variety of manufacturing environments and reliably supports subsequent processes such as bonding, coating, painting, or conversion treatments.”

Cooler baths, lighter wastewater

Dr. Thomas John-Schillings, Technical Manager for Henkel's Multi-Metal Surface Treatment, Cleaners and Lubricants business, locates the central sustainability case in how the builder and the surfactant work together.

“The central sustainability benefit of BONDERITE C-AK 5831 ECO lies in the interplay between the mildly alkaline builder and specially formulated low-temperature surfactant additives. This combination,” he says, “enables highly effective cleaning at temperatures of just 30°C to 40°C.”

Low temperature usually means a weaker clean, so the claim needs a hard test. John-Schillings offers one. “Even demanding, high-viscosity contaminants, such as hot-melt residues, can be reliably removed without leaving any residue. Because the bath temperatures are lower than those of conventional cleaning processes, energy consumption can be reduced, thereby contributing to a lower CO₂ footprint.”

Depending from the individual production and application conditions at the customer, energy reductions of up to 15 per cent for every 10-degree reduction in spray application may be possible. Moving from the conventional window to the low-temperature one spans roughly two such steps, though the potential saving in any plant will depend on the respective individual line.

“Furthermore, the product’s mildly alkaline setting can simplify wastewater treatment,” says John-Schillings. “Compared with strongly alkaline cleaning systems, the need for neutralisation and precipitation chemicals can be reduced. In addition, a more favourable ratio of rinse water to process wastewater can help lower the overall wastewater treatment effort.”

“In addition, the borate-free formulation offers important advantages in the area of health, safety and environmental requirements. Eliminating borates helps companies meet increasing occupational and environmental protection requirements and contributes to a more sustainable process design, while through lower etching, it leads overall lower sludge generation.”

Losing borates without losing control

Historically, dropping borates has meant accepting less control over etching, and that matters most on aluminium, where every micron removed changes the surface. A 1 per cent solution of this cleaner sits at a pH of about 8.2, well away from caustic territory. The additives themselves remain unnamed, but Harb describes what they do. “The low etching effect is achieved through the mild pH value and the use of special additives. This combination makes it possible to limit material removal to the minimum required for the process without the use of borates.”

One cleaner for a mixed-metal line

Lightweight construction has put steel, galvanised coatings and aluminium onto the same line, often within the same hour. Harb is precise about what that does and does not guarantee.

“The product is suitable for use on a wide range of metallic substrates. However, given the diverse material and process requirements, its suitability should always be evaluated with regard to the subsequent manufacturing steps, such as bonding, coating, or conversion treatment, in each specific application.”

Henkel, confident in its solutions, backs that caution with specifics. It lists steel, hot-dip galvanised and zinc-magnesium coated substrates alongside aluminium alloys, which it names as the preferred target.

Henkel recommends application-specific pretesting to ensure compatibility with the respective substrate and subsequent process steps.

“Multi-metal capability is becoming significantly more important in light of the lightweight construction trend and the increasing combination of different materials in modern production lines. BONDERITE C-AK 5831 ECO was therefore designed to be as versatile a cleaner as possible. Its mild alkalinity supports the gentle cleaning of various surfaces. Nevertheless, every system is unique: the material mix, type of contamination, process management, and subsequent treatment steps must be evaluated through preliminary trials in order to define the process parameters for each specific application and to ensure consistent cleaning performance.”

Regulation tightens the screw

For many suppliers, borate-free is shifting from a preference to a procurement condition. Harb names the main driver.

“A key framework is compliance with the requirements of the European chemicals regulation REACH. In addition, many OEMs and suppliers implement their own substance restrictions, purchasing requirements, and sustainability targets. Borate-free and more resource-efficient formulations help customers meet both regulatory requirements and internal specifications.”

Part of a longer direction

Harb frames the product as a marker on a longer road rather than a one-off.

“BONDERITE C-AK 5831 ECO exemplifies our ongoing ambition to advance cleaning performance and sustainability hand in hand. Our aim is to provide customers with high-performing solutions that also help reduce reliance on increasingly scrutinised ingredients and unlock potential in energy demand, process chemistry, and wastewater treatment. Its continued development is guided by the real-world process requirements of our customers, as well as by evolving regulatory and internal company standards.”

Switching without stopping the line

For a Tier 1 supplier running a conventional alkaline cleaner, the practical question is what a change costs in disruption. John-Schillings is direct about how it should begin and who helps. “A product change should always be evaluated on the basis of the specific materials, contaminants, system conditions, and quality requirements. Henkel accompanies the entire conversion process: from the first technical discussions through approval testing and laboratory trials to the actual changeover and support in production."

“Our technicians provide on-site assistance until the process can be handed over in a stable state, and they remain available for later optimisations as well. Our goal is to help customers achieve their sustainability, quality, and cost targets together.”

Looking beyond the tank

John-Schillings closes with an insight into treating any cleaner as a standalone fix.

“The cleaner is an important building block, but only one step within the overall manufacturing process. Additional optimisation potential often arises when upstream process steps, existing surface residues, and the interactions with the subsequent pretreatment are also taken into account. Henkel can support and analyse processes holistically along the entire value chain, from forming through pretreatment to bonding and sealing. This cross-process expertise helps us identify dependencies between the individual process steps and, together with the customer, unlock further improvements.”

He even adds a digital tool to the offer. “With the extension of the Henkel Environmental Assessment Reporting Tool (HEART), Henkel also now offers its customers a distinctive digital service for process planning, evaluation, and optimisation of the use-phase. The tool enables the modelling of existing processes, the comparison of alternative scenarios, and the transparent assessment of CO₂, energy, water, consumption, and ultimately cost effects."

“Using HEART (use-phase), Henkel’s process experts support customers in identifying optimisation potential at an early stage and in making well-founded decisions for more sustainable and more economical production processes.”

Few plants would list the cleaner stage among their strategic decisions. A bath running up to 20 degrees cooler, with fewer neutralisation chemicals leaving through the wastewater plant, suggests it deserves a seat at that table. A sensible first step is to model the current line before touching the chemistry.