2. Chemical conversion
•A chemical manufacturing process in which chemical transformation takes place, that is, the product differs chemically from the starting materials. Most chemical manufacturing processes consist of a sequence of steps, each of which involves making some sort of change in either chemical makeup, concentration, phase state, energy level, or a combination of these, in the materials passing through the particular step

3. Chemical conversion involves different types :
1-Chemical or electrochemical conversion treatment that produce complex phosphates, chromates/oxides on metal surface
*phosphates coating is the treatment of Fe ,steel , galvanized steel and Al with dilate solution phosphoric acid in the surface of these metals. The phosphates coating range in thickness from less than 3 to 50 μm
this coating depend on (method of cleaning before treatment , use the activating rinses containing Ti and others metals ,method of applying solution ,temperature, concentration and duration of treatment

4. The weight and crystalline structure of the coating and the extent of penetration of the coating into the base metal can be controlled by :
Method of cleaning before treatment
Use of activating rinses containing titanium and other metals of compounds
Method of applying the solution
Temperature, concentration, and duration of treatment

6. Types of phosphate coatings
Three principle of phosphate coatings in general use, there are : 1-Zinc phosphate coatings 2-iron phosphate coatings 3-manganese phosphate coatings

7. Applications
The greatest use of phosphate coatings use is as a base for paints, phosphate coatings are also used to provide : 1-a base for oil our other rust-preventive materials 2-lubircity and resistance to wear , galling or scoring of parts that moving in contact with or without oil 3-a surface that facilitates the cold forming 4-short time resistance to mild corrosion 5-a base for adhesive in plastic –metals laminations

8. Chromates coating
Chromates coating: are formed by a chemical or electrochemical treatment of metals in solutions containing hexavalent chromium (Cr+6).
The process results in the formation of an amorphous protective coating composed of the substrate, complex chromium compounds, and other components of
the processing bath.
* Chromates conversion coating are applied to enhance corrosion resistance ,improve the adhesion painted and decorative finish . And this may be applier by immersion, spraying and other methods such as brushing to special cases

9. Chromate coatings are applied by contacting the processed surfaces with a sequence of processing solutions. The processing baths are arranged in a series of tanks, and the surfaces to processed are transferred through the sequence of stages by using manual, semiautomatic, or automatic control. The chromate coatings are usually applied to metal parts or to a continuous metal strip running at speeds to 5 m/s (1000ft/min).
Wastewater treatment sludges from chromating operations are considered hazardous waste. As a result, the use and disposal of chromium and chromium compounds have received much regulatory attention because of the toxicity of chromium and indications that it is a cancer-causing agent.

10. Aluminum Anodizing
Aluminum anodizing is an electrochemical method of converting aluminum into aluminum oxide (Al2O3) at the surface of the item being coated. It is accomplished by making the workpiece the anode while suspended in a suitable electrolytic cell. Although several metals can be anodized, including aluminum, titanium, and magnesium, only aluminum anodizing has found widespread use in industry.
The broadest classification of types of anodize is according to the acid electrolyte used. Various acids have been used to produce anodic coatings, but the most common ones in current use are sulfuric (H2SO4) and chromic (CrO3) acids. There are two types of H2SO4 anodizing. The first is a room-temperature H2SO4 process termed conventional anodizing, and the second is a low-temperature H2SO4 process termed hardcoat anodizing.

11. Pack cementation diffusion treatments
Pack cementation is a batch process that has been used to produce corrosion-and wear-resistant coatings on inexpensive or otherwise inadequate substrates.
Pack cementation is a widely used chemical vapor deposition technique that confers oxidation resistance on ferrous alloys. Usually relatively expensive aluminum or binary alloys grade reagent is used during the pack process with aluminum as a source.
Pack cementation is the most widely used as it is inexpensive and well adapted to coating of small parts.

12. This process includes
1-Aluminizing 2-Chromizing 3-Siliconizing The traditional pack consists of four components: *Substrate or parts to be coated *Master alloy (Cr and/or Al, Cr and/or Si) *Halide salt activator *Relatively inert filler powder (Al2O3, SiO2, or SiC)

13. Pack cementation aluminizing is the most widely used coating process
Pack cementation aluminizing is the most widely used coating process. Corrosion resistance of aluminidecoatings can be increased by modification with chromium, platinum, or silicon. Chromium diffusion coatings can be used at lower temperatures.
In this process, the components to be coated are immersed in a powder mixture containing Al2O3 and aluminum particles. About 1-2 wt% of ammonium halide activators are added to this pack. This is then heated around °C in argon or H2 atmosphere. At these temperatures, aluminum halides form, which diffuse through the pack and react on the substrate to deposit Al metal.

14. Variables that affect the coating process include:
•Substrate composition •Powder bed composition •Heat treating conditions •Time •Furnace atmosphere

15. advantages
Non-line-of-sight process for uniform coatings on complex shapes
Batch process can coat hundreds of parts simultaneously
No unique equipment required to establish coating capability
Technology can be easily transitioned to industrial production

16. Applications
Pack cementation and related diffusion coatings serve well for most aircraft engine applications. The trend for industrial and marine engines is more toward the use of overlay coatings because of the greater ease of designing these to meet a wide variety of corrosion conditions

17. Surface modification by ion implantation
Ion implantation is a material surface modification process by which ions of a material are implanted into another solid material, causing a change in the surface physical and chemical properties of the material
Ion implantation is a surface modification process in which ions are injected into the near-surface region of a substrate.

19. High-energy ions, typically 10–200 kiloelectronvolts (KeV) in energy, are produced in an accelerator and directed as a beam onto the surface of the substrate. The ions impinge on the substrate with kinetic energies 4–5 orders of magnitude greater than the binding energy of the solid substrate and form an alloy with the surface upon impact. Virtually any element can be injected into the near-surface region of any solid substrate. Commonly implanted substrates include metals, ceramics, and polymers. The most common implanted metals include steels, titanium alloys, and some refractory metals

20. Advantages
Produces surface alloys independent of thermodynamic criteria
No delamination concerns
No significant dimensional changes
Ambient-temperature processing possible
Enhance surface properties while retaining bulk properties
High degree of control and reproducibility

21. Limitations Limited thickness of treated material High-vacuum process
Line-of-sight process
Alloy concentrations dependent on sputtering
Relatively costly process; intensive training required compared to other surface treatment processes