Electrolytic Plasma Technology [EPT], is an effective surface engineering tool that combines the cleaning and coating of metals. During EPT processing, DC voltage is applied to the electrodes in an aqueous electrolyte, which produces plasma at the surface of the work piece. Thermal, chemical, electrical and mechanical effects imparted by EPT to the work piece create unique surface characteristics.
When utilized for the cleaning of metals, Electrolytic Plasma Technology effectively removes scale, dirt, rust, lubricants, and other types of contamination from the surface. In addition, the surface of the metal is left with a micro-rough profile structure that greatly enhances adherence properties for coating.
EPT is an environmentally friendly process that eliminates the need for harmful acids or chemicals that could be hazardous to both workers and the environment.
Electrolytic Plasma Technology deposits dense, conformal coatings to various metals and alloys. These coatings can be deposited at rates of up to 2 μm/sec. and thickness of the coating can be controlled as per the needs of the customer. The adhesion characteristics of CAP applied coatings are very high and coated materials can be formed, and even drawn, without worrying about delamination of the coating. EPT coatings can be applied as pure metals, layered metals, or alloys, and can be applied to materials of a large variety of shapes and sizes.
Mechanical Properties such as tensile, torsion and ductility properties are not altered during the EPT process. The coating forms a metallurgical bond with the substrate which gives it excellent adhesion. In addition, no brittle intermetallic layers are formed in the coating (below).
EPT coatings are very effective against corrosion. In fact, EPT coatings from CAP have been proven to last twice as long as HDG coatings of comparable coating weights in salt spray tests (According to ASTM B117).
Surface morphology of the coating eliminates the use of borax, phosphating, or other lubricant carriers during drawing. It also helps us in directly drawing a rod to a small wire size.
The CAP process uses electricity and benign electrolytes for cleaning, eliminating the need for strong acids. This greatly reduces the cost of the process by reducing/eliminating the need for toxic materials handling, storage, and disposal of these harsh chemicals.
At present, the metal industry offers many options for the cleaning and coating of metals. Listed below are some of the reasons the CAP process should be considered when searching for an alternative to the more conventional methods.
Only benign Salts (NaHCO3) and water are required
Large volumes of hydrochloric acid, sulfuric acid, and/or nitric acid are often used.
Additional chemicals treatments are not needed. No need for neutralization or redundant rinse systems
Lime, borax, and ZnSO4 are needed to neutralize, preserve, and/or provide a lubricant carrier.
handling/disposal of hazardous liquids
CAP's cleaning process uses no chemicals that are considered hazardous.
Large amounts of harsh acid, rinse water (acidic), and other chemicals must be neutralized, disposed of, or reclaimed.
solid waste byproducts
A fine textured scale powder (iron oxide) is the only byproduct of cleaning; a simple filtration system is all that is needed.
A toxic acidic sludge must be handled, stored, disposed of, and/or processed for acid reclamation.
Basic treatments methods for metal include Electrical (E), Thermal (T), Chemical (C) and Mechanical (M). Existing technologies include combination two or three of these methods. As illustrated below, the CAP process combines all of the basic treatment methods, thereby increasing its effectiveness.
Combinations of Methods
Surface profile of a material is important for various industrial applications for example to obtain adhesive coatings. Plasma processing of materials provides a capability to control surface profile easily by varying processing parameters and the aqueous electrolytic media.
Time required for cleaning and coating is less than other conventional operations resulting in a smaller operation. In cleaning of steel wire having patented scale, in line cleaning speeds up to 180 ft/min have been achieved. In coating, generally, the deposition rate is approximately 1-2 μ/sec, which can be controlled by process parameters.
In line capability of cleaning and coating makes this technology time efficient and could eliminate the need for large batch processing areas in certain applications, such as the pickling of wire rod.
The CAP process can be used to clean and coat metals of various size and shapes. Please visit the products section for details.
The CAP process is simple and requires less floor space as compared to conventional cleaning methods such as acid cleaning.
CAP's EPT process has been proven NOT to cause hydrogen embrittlement (HE) of the work piece. These tests were conducted as per the specification of ASTM F519-05.
Hydrogen embrittlement (HE) is a real concern due to the steel absorbing hydrogen. This jeopardizes the strength of the steel. Additional measures must be taken to prevent/reverse this process.
loss of steel
CAP's process does not cause any significant loss of steel. In fact, it is estimated that 30-40% of the scale is reconstituted to alpha-iron and deposited back to the surface
Pickling typically causes between 2%-3% loss of the steel. This can be prevented with other chemical additives, but these chemicals add to the bottom line.
100% cleaning capability
CAP's process can clean steel to 100% with no material loss.
Pickling generally cleans to a level of ~95%. At this point the acids attack the base metal resulting in loss of the product.
Other than filtration and consumables, maintenance of the CAP process is minimal.
Requires constant monitoring and maintenance of acid solution. A delicate chemical balance must be kept for efficiency of the process.