Colorful doesn’t have to mean expensive
could be our motto for when our customers request almost every possible surface treatment under the sun. We don’t immediately have to reach for the file on electrophoretic deposition (as occasionally happened in the past without our knowledge) to guarantee that parts will be delivered rust-free to our customers – which typically then forces those customers to laboriously remove that deposited layer, down to the last paint chip, by sandblasting. The problem of preventing corrosion during transport can be solved far more simply with other methods. However, electrophoretic painting or cathodic electrodeposition have their uses, and are two among many possible methods of surface finishing.
Cathodic electrodeposition (CED) is an electro-chemical process in which an object is submerged in a water-based lacquer under the influence of an electric field; typically, this field is produced by DC of 3,000 ampere and 220 to 290 volts. CED coatings are free of heavy metals (i.e., lead) and are black (similar to RAL 9005). The thickness of the coating that remains on the part depends on part geometry, but is generally between 10 and 40 µm. After applying a thin coating layer, surplus liquid is removed with a rinse.
In a following step, the coating is “baked on” in a CED drying furnace for 20 minutes at 230° C (445° F). The coating then cross-links chemically to form a thin, homogenous film on the part surface, producing a surface that is resistant to both corrosion and negative effects of acidic/basic solvents.
Liquid Coating (Painting)
Paint or lacquer comprises a mixture of non-volatile particles suspended in a volatile solvent. The solvent evaporates after coating (during the drying process); the non-volatile component of the solution remains and forms a smooth film on the surface of the painted object. These non-volatile components may be binders, pigments, oils, resins, fillers, or other additives. The binder ensures the even distribution and suspension of pigments and solvent in the paint, contributes to optimal drying (prevents formation of air bubbles), and is responsible for the “shiny” gleam on the part surface after drying.
The electro-chemical deposition of a thin layer of metal on the surface of another material is known as galvanizing. This process plays an important role in improving the corrosion resistance of iron and steel components, but it can also be used to improve the hardness or surface slip properties significantly (as chrome coatings do). The physical principles are fairly simple: electrical current is applied to an electrolytic solvent bath. The metal used for the coating is located at the positive pole (anode); the casting to be coated is located at the negative pole (cathode). The current dissolves metal ions from the “sacrificial” electrode, which are deposited on the surface of the casting via reduction. The longer the casting spends in the bath and the higher the current is, the thicker the metal layer becomes. The process is differentiated according to the material used for coating (the substrate): Bronzing, chrome-plating, chromate conversion coating, phosphate coating, and zinc-plating. In principle, all cast iron materials are suitable for galvanizing processes; in some cases, however, it may be more cost-effective depending on the end goal to consider switching materials – for example, exchanging SG cast iron for ADI in order to obtain better surface hardness values.
High-temperature materials have established themselves as one method of insulating motor components such as exhaust manifolds; their use can reduce surface temperatures from as much as 600° C (1110° F) down to 200° C (390° F). For this type of insulation, a fiberglass insulation shell (typically 1-2 cm thick) is attached to the casting and held in place by two thin stainless-steel sheets (0.1 mm thick). The configuration is pressed into its final position, and the two halves of the stainless steel layer are then joined by micro spot welding. In addition to absorption of acoustic vibrations, a higher temperature is also obtained in the exhaust gas line during the motor’s ignition and warm-up phase, which in turn reduces NOx and CO2 emissions.
We will find a suitable solution.