Alkaline degreasing baths

Degreasing baths remove oil and other pollutants from the surface of metal components before this surface is treated. In due time the contents (1-2 m ) of the degreasing bath become polluted and have to be exchanged for fresh cleaning solutions. This poses several problems  

Most often these actions are performed by specialised firms. 

Tj ical lifetimes of degreasing baths amount to 1-2 weeks. By drawing a continuous stream from the degreasing bath, and circulating it over a microfiltration system and concentration tank, oil and dirt can be retained in the concentration tank. 

Microfiltration with HIC s 0.2 xm membranes yields average fluxes of 250 1/m h at temperatures from 40 to 70°C the pH lies between 9 cmd 11. The permeate contains less than 100 ppm oil. This treatment extends the life time of the degreasing bath up to five times pay back time is less than two years. Similar data are reported of Carbosep, Le Carbone Lorraine and Atech membranes [19,22,37,38]. 

In these processes the retention of the detergents has to be monitored in order to keep their concentration in the degreasing bath at the correct level. 

---

Uses Surfactant for shampoos, bath prods., personal hygiene preps. pharmaceutical ointment base, surfactant, emulsifier dispersant for alkaline degreasers foam booster/stabilizer for shampoos, bubble baths, liq. soaps thickener used with anionic surfactants foaming agent, conditioner, vise, booster, wetting agent in textile finishing... 

In this procedure the first step, once again, is to pickle the aluminium substrates in accordance with the specifications quoted above. Under certain circumstances it may be sufficient to use only an alkaline degrease before anodising. The etched panels are then clamped to the anode of a standard anodising bath and are immersed in a solution of phosphoric acid at 25°C. Anodising then takes place in accordance with one or other of several European and American specifications [29,30]. A typical bath composition is ... 

The alkaline peroxide etch, dependent on bath conditions, gives an oxide thickness of 60-200 nm. The process comprises a 3-5 min alkaline degrease in Kelite 19 at 60-71°C. The washed components are then immersed for 23-27 min, at 55-65°C, in a bath containing 0.5 M sodium hydroxide and 0.4 M hydrogen peroxide (H2O2). The etched substrates are then washed and air-dried at 65°C. 

Alkaline cleaning is effective for removing the water-dissolvable contaminants that may be difficult to remove with solvent wiping. Substrate immersion in an alkaline bath sometimes follows solvent degreasing. Parts are continuously agitated in a water solution maintained at 77-93°C and at an alkaline pH. As dirt, metal chips, and other contaminants are removed, more alkaline solution must be added to maintain the pH, and the bath must be replaced if contaminant levels become too high. 

Various metals, such as aluminum and zinc, are added to the zinc bath to modify the coating. Addition of aluminum produces an even coating and addition of tin improves adhesion. Fluxing is necessary to absorb the impurities on the surface and to ensure that only clean steel comes in contact with molten zinc. In the dry process, the workpiece is first degreased in a hot alkaline solution, and rinsed with hot and cold water, respectively. After rinsing it is pickled in HCl or... 

The aluminium foil, which is coated in rolling oils, is first degreased/etched using an aqueous alkaline solution of Ridoline 72 (sodium hydroxide NaOH) or, better, Ridoline 305 (potassium hydroxide KOH). The use of potassium hydroxide allows a lower bath temperature to be used — generally about 55°C. 

Uses Nonrewetting wetting agent in formuiated degreasers, polishes, fabrics Features Low foaming, alkaline stable, and is bath compatible with optical bright-eners and UV absorbers... 

Uses Surfactant In emulsion polymerization, healthcare industry, textile industry, shampoos, bubble baths, liq. hand soaps, degreasers, alkaline scouring, car washes solubilizer for nonlonics... 

Uses Surfactant, emulsifier, solubilizer in detergent formulations for dry cleaning, chlorated detergents and degreasing agents for automotive parts emulsifier for hair dyes, permanents and bleaches, lotion, deodorants solubilizers for bath oils Features Moderate foaming power reduces surface tension does not precipitate in the presence of ions in hard water maintains chemical, physical stability in alkaline or acid environments compat. with non-ionic, anionic, cationic surfactants... 

Short-chain (Cg-Cio) alcohol sulfates are technical wetting agents (insensitive to water hardness and electrolytes, l drotropic properties) and are preferably used in stronger alkaline media, e. g., merceri-zation baths in - textile auxiliaries, in cleaning and degreasing, electro-plating baths. 

Aqueous degreasing processes use alkaline or acid solutions containing chemicals and various additives. These baths become contaminated with oil and when the bath loses its efficiency, its contents have to be renewed, at a high cost, or the oil must be removed. A well tested method for oil removal is based on using CFCC (carbon fibre-carbon composite) filter membranes, and permanently hydrophilic polymer membranes. 

---