SMLease Design

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Blog posts : "plating"

Chromate Conversion Coating - SMLease Design

Chromate conversion coating is a type of conversion coating used to passivate zinc-plated Steel, aluminium, copper, silver, magnesium and tin alloys parts to provide protection from white rust or red rust.

Chromate conversion coating is primarily used as a corrosion inhibitor, primer, decorative finish or to retain electrical conductivity. Chromates can come in many different colour variations: clear, blue, yellow, or black. 

Chromate conversion Coating Specifications:


Class 1A - (Yellow) Maximum Protection against corrosion, Painted or unpainted

Class 3 - (Clear or Yellow) For protection against corrosion where low electrical resistance is required

MIL-DTL-5541F / MIL-DTL-81706B


Type I (Hexavalent Chro…

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Effects of Anodising on radiant heat transfer in heat sink

Heat sinks cooled by natural convection may benefit from an anodized finish, but the added cost of the finish may not be justified when the part is used in forced convection cooling.

Surface emissivity limits the amount of heat transfer due to radiation cooling. With 1.0 being perfect (black body) emissivity anodized aluminum is 0.85 and unfinished is 0.05.

Heat transfer due to radiation is proportional to the heat sink surface area exposed to its surroundings and to the temperature rise above ambient (in absolute °K) raised to the 4th power (T Heat-sink Tambient)4. In natural convection on small heat sinks with open fins, and a high benefit from anodizing by up to 45%.

Relatively large extrusions and those used at low temperature rise, as in many high power applications, wil…

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Aluminium Chromate Conversion Coating - SMLease Mechanical Design

The chromate process provides a clear iridescent to slightly golden iridescent film of low contact resistance.  

Aluminium chromate conversion coatings improve the corrosion resistance of wrought, heat treatable and cast aluminium alloys while providing an excellent base for subsequent painting or powder coating services.

  • Aluminium chromate conversion coatings, often referred to as chemical film or under the trade names Alodine or Irridite, produce a thin coating in the range of 0.25 - 1 microns in thickness.
  • Aluminium chromate conversion coatings are amorphous in structure with a gel-like composition hydrated with water. This characteristic provides aluminium chromate conversion coatings with a unique self-healing characteristic if scratched or abraded.  Metal exposed from a s…

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