Apticote Hard Anodising

The Apticote 300 process is a unique approach to precision hard anodising (or hard anodizing). Poeton provide a level of quality control, combined with high through-put and low turn-round times, that is unmatched by our competitors. Poeton offer a wide range of hard anodising variations, one of which will satisfy you particular requirements for wear resistance, corrosion protection and mechanical properties. Our strength lies in the skill of our operators, with your component being processed exactly to your requirements, irrespective of the alloying content of the alloy. Specifically, the highly innovative Apticote 300M hard anodising process gives a layer thickness twice that which is normally achievable, producing excellent thermal and electrical insulation properties.
The APTICOTE 300 Options APTICOTE 300N For maximum hardness and wear resistance APTICOTE 300W For improved fatigue strength APTICOTE 300A and 300D For maximum fatigue strength combined with corrosion protection APTICOTE 300M For greatest coating thickness

Features High hardness Very low wear Excellent corrosion protection Superb control of coating thickness Uniform coverage No post-machining Coats a range of aluminium alloys Pleasing visual appearance and feel Apticote 350 and 370 series give low friction, good release and non-wetting properties		Coating cross-section, x 1000 The protective film is created on, and within, the surface of aluminium and its alloys. The greater thickness and wear resistance of Hard Anodising compared with Chromic or Sulphuric Anodising make it the natural choice for preparing aluminium for use in more arduous environments

Applications Apticote 300 hard anodizing is used in a wide variety of industries, including: Gears Pulleys Valve Blocks Hydraulics Pneumatics Pistons Hinges Swivel joints Rod ends Food Chutes Nozzles

Performance Benefits

• Excellent Wear Resistance

  Tests show that, for certain aluminium alloys, the wear resistance of Apticote 300 hard anodising is similar to that of case-hardened steel and even that of Hard Chromium, although the micro-hardness values (reflecting the micro-cellular structure rather than actual base oxide) are only 300-500 VHN. At low loads, the wear compares favourably with that of tool steels having a hardness rating of 950 VHN. Load-carrying capability is dependent upon alloy choice. The benefit to the end-user is prolonged wear life with a substrate that provides for reduced weight and cost.

• Good Corrosion Protection

  Generally superior to that of chromic and sulphuric anodising (where the thin coating may be easily scratched or damaged), the corrosion resistance of Apticote 300 hard anodizing can be further improved by dichromate or acetate sealing, although there will be some loss of abrasion resistance. Typical results show >500 hours salt spray endurance on 2024 aluminium alloy. Note that alloys with a lower copper or silicon content show a lower resistance to corrosion. The benefit to the end-user is prolonged corrosion protection with a substrate that provides for reduced weight and cost.

• Good Heat Resistance

  Apticote 300 hard anodised coatings can withstand short exposures up to 20,000DegC, which makes them ideal for parts like rocket venturi. Long exposure to high temperatures has no adverse effect on the coating performance, other than crazing of the surface. Specifically, Apticote 300M, with a thickness over 200µ, is a very effective thermal barrier, and it out-performs any other anodised layer in rocket venturi applications

• High Dielectric Strength

  Breakdown voltage increases with film thickness. Coatings normally withstand voltages in excess of 1,000volts DC. Unlike most insulators, Apticote 300 hard anodised coatings can operate at temperatures up to 5,000DegC. Its combination of high dielectric strength and thermal stability make Apticote 300 the ideal surface for mounting electrical components.

• Mechanical Strength/Fatigue Strength

  Losses in tensile strength due to anodising are very slight and have not prevented the widespread use of aluminium into many high-tech industries. However, anodised aluminium is not recommended for high-impact situations. Hard anodising can reduce the fatigue strength of the base material by up to 47%, depending on the alloy and the coating thickness. However, this loss can be held at 16-20 % by modifying the sealing procedure, provided a little reduction in abrasion resistance can be tolerated. Where fatigue mechanisms exist, the components benefit from ceramic shot peening before coating.

• Uniform Coverage

  Apticote 300 hard anodising provides a uniform surface layer of predictable thickness. Component surface growth is approximately 50% of the total coating thickness, so that final dimensions can be accurately predicted. For optimum results, sharp corners should be relieved as far as possible. The benefit to the end-user is reduced machining and grinding costs and improved precision of manufacture.

  Poeton are highly skilled at jigging and fixturing, so that an even coating distribution can be achieved on complex geometrical features, including down long bores, where normal anodised layers will thin.

  However, it should be noted that anodising to a specific final size requires that the as-manufactured dimensions and tolerance band are both closely controlled. Tolerances are additive, so that the final size depends more on the incoming precision than on any small variations in the anodising process. Poeton strongly recommend that parts should be anodised to a specified coating thickness rather than to a defined final size.

• Coating Growth

  Like all anodising processes, as stated above, Apticote 300 grows both in and out from the original surface. Whilst the nominal outward growth is usually taken as 50% of the coating thickness, the precise amount varies with the alloy composition, as shown in the table.

  In the table, the dimensional change is the increase in size at the single surface as a % of the coating thickness, i.e. the 'out' growth. So, for instance, with the Cu containing alloy, the layer will grow 43% out and 57% in.

• Substrate materials

  Apticote 300 hard anodizing can be applied to a range of aluminium alloys. Best results are obtained on alloys in which the Si content is below 10% and the Cu content is below 5%.

  As examples, alloy types HE30 (6082), L65 (2014), L160 (7075), DTD 735 and LM25 are particularly responsive to the Apticote 300 process.

• Colour

  Colour matching of hard anodised parts is near impossible, with too many variables on the parts, their method of manufacture, their heat-treatment, as well as in the details of the process, all conspiring to produce unpredictable changes in hue and shade. Poeton do not, therefore, offer colour matching with Apticote 300.

Technical Data Sheet

Please click here if you would like further information from our technical data sheet (PDF = 140KB).