Requirements for the anode coating according to GOST 9.303-84

GOST 9.303-84 establishes general requirements for the selection of metallic and non-metallic coatings of parts and assembly units, which cause chemical, electrochemical and hot (tin and its alloys) by methods, including, to aluminum anodic oxide coatings.

The numbering of the items – GOST 9.303-84.

Requirements for base metal

11. General requirements for basic metals and coatings must comply with GOST 9.301-86.
processes produce coatings operations by electrochemical and chemical methods are set GOST 9.305-84.

Anodizing holes and channels

13. Surface in blind and / or narrow holes, small channels, gaps and cracks details, wherein the electrochemical coating according to GOST 9.301-86 may be missing, It must be protected from corrosion lubricants, Paint, etc..

Anodizing welds

15. On items with welded seams, which are formed gas arc welding, and details, having brazed joints, be applied to electrochemical and chemical coatings provided continuity and integrity of a welded or soldered seam around the perimeter, preclude wicking of electrolyte into the gaps or pores.

Increasing the size of parts during anodization

17.1.1. about increase with the size of anodizing parts 0,5 coating thickness (per side).

Effect purity aluminum surface quality anodizing

17.1.2. Quality of the anode-oxide coating increases with the improvement of the surface treatment of parts purity.

Filling anodizing

17.1.3. Anodic oxide coating, It is used for corrosion protection, exposed filling in potassium dichromate solution, sodium bichromate or in water depending on their purpose. These coatings provide a good basis for the application of coatings, adhesives, sealants, etc.. P. To give the decorative details of the form of the anode-oxide coating prior to filling dye adsorption process in solutions of various dyes or electrochemically in a solution of metal salts.

Specular aluminum anodizing

17.1.4. For details on the anodized aluminum alloy gloss is recommended to polish the surface. The reflectivity of anodized aluminum and its alloys decreases in the following order: A99, A97, A7, a6, AD1, AMg1, AMg3, AD31, AD33.

solid anodised

17.1.5. Solid anodic oxide coating having a thickness 20-100 microns are wear-resistant (especially when using lubricants), and also possess heat- and electrical insulation properties.
Details with hard anodic oxide coatings can be machined.

The cracking of the anode coating when heated above 100 oC

17.1.6. Anodic oxide coatings have a porous structure, not electrically conductive, brittle and prone to cracking when heated above 100 ºC or deformations.

Increased surface roughness during anodization

17.1.7. With sulfate anodizing, the surface roughness increases by two classes; chromic acid anodizing affects the surface roughness to a lesser extent.
when assigning anodic oxide coatings, consider the impact on the mechanical properties of the base metal. Effect of the anode-oxide coating increases with increasing film thickness and depends on the alloy composition.

Anodizing in chromic acid

17.1.8. Anodizing in chromic acid is usually used for corrosion protection of aluminum alloy, containing not more than 5 % copper, mainly, for details 5-6 qualifications (1-2 classes of accuracy).

electrical insulating anodized

17.1.9. An.Oks.eiz coating is applied to make the surface of aluminum parts or aluminum alloy electrical insulation properties.

17.1.10. When the insulating anodizing electrolyte recommended oxalate.
The coating provides stable electrical insulating properties after impregnation or application of appropriate paints and varnishes; during impregnation, the thickness of the material increases by 3-7 m, when applying paint - to 80 m.
Resist coating breakdown increases with its thickness, decrease the porosity and increase the quality of the original surface.

scratches, risks, dents, sharp edges reduces electrical properties of the coating.

After impregnation varnish coating insulating resistance the breakdown depends, mainly, thickness of the coating and little dependent on the composition of the aluminum alloy and process of anodization.

17.1.11. Coating An.Oks.emt recommended for parts of low alloy wrought aluminum alloy with the purpose to impart a decorative kind.

duralumin anodizing

17.1.12. for details, made of alloys, containing more 5 % copper, not recommended for coating and An.Oks.hrom

17.1.13. for details, made of alloys, containing more 3 % copper, not recommended for coating and An.Oks.emt An.Oks.eiz.

The hardness of the anodic coating

17.1.14. Anodic oxide coating has strong adhesion to the base metal; has a lower thermal conductivity, than the base metal; resistant to mechanical wear. The microhardness of the alloys D1 to brands, D16, B95, Ak6, AK8 is 1960-2450 MPa (200-250 kgf); on A5 alloys, A7, A99, AD1, AMg2, AMg3, AMg5, AMg6, AMC, AB - 2940-4900 MPa (300-500 kgf).

These materials are provided for information only with GOST 9.303-84. For full professional use must be used, it's desirable, actualized in the standards bodies, standard text.