Andrews Powder Coating Inc also offers metal plating services. In many cases, it is advantageous to plate the metal prior to powder coating
for an extra layer of corrosion barrier, or to provide additional adhesion qualities.
Chromate Conversion/Chem Film Over Aluminum Parts
Clear,Gold & Black Zinc Over Steel Parts
Decorative Nickel & Electroless Nickel
Clear Baked Enamel
Barrel (Copper & Brass)
Chem Film (also called Chromate Conversion Coating and by the brand names Iridite and Alodine)
Chem Film is a chemical conversion process that produces a protective chromate surface corrosion resistant film on aluminum and aluminum alloys. Chem Film also acts to passivate the aluminum. Passivation is the chemical neutralization of contaminant iron in the surface of the aluminum or aluminum alloys. Iron is typically transferred by tooling during formation of the aluminum in the mill. The coating can be applied with or without color, the darker coatings providing the greatest corrosion protection. It is usually specified either “clear”, meaning with no color, or “gold”. There are two types of Chem Film: Hexavalent and the less toxic and RoHS (Restriction of Hazardous Substances) compliant Trivalent formulation.
Military Specifications (MIL-SPEC) for Chem Film are:
MIL-C-5541E Type I - Hexavalent Chromium.
MIL-C-5541E Type II – Trivalent Chromium
There are two classes of Chem Film Coatings:
Class 1A – Used to provide corrosion protection for painted or unpainted surfaces.
Class 3 – Used to provide corrosion protection on parts requiring low electrical resistance.
The following MIL-SPEC also applies with the same types and classes:
These specifications are approved for use by all departments and agencies of the Department of Defense.
Zinc: Black, Clear and Gold coatings for ferrous metals only. Bright or dull finishes are offered. Zinc plated products are very resistant to rust due to the Noble metal characteristics of the zinc. Nickel is an acceptable undercoating for extreme corrosion resistant properties
TYPE I: No Supplemental treatment.
TYPE II: Supplemental Yellow Chromate treatment. The primary use of chromate finish on Zinc is to retard or prevent formation of white corrion products on Zinc surfaces.
TYPE III: Supplemental Clear Chromate treatment. The primary use of chromate finish on Zinc is to retard or prevent formation of white corrion products on Zinc surfaces.
TYPE IV: Supplemental Phosphate treatment. The primary purpose of phosphate coating on Zinc is to proved a paint base.
CLASS SC1: .00020" internal electronic hardware
CLASS SC2: .00031" external cabinetry
CLASS SC3: .00051" severe service environment
CLASS SC4: .00098" very severe service environment
There is a nickel finish for almost any need. Nickel can be deposited soft or hard - dull or bright, depending on processes used and conditions employed in plating. Decorative nickel plating can have an appearance of stainless steel in color, while some proccesing can create a dull grey or light grey (almost white) color. Corrosion resistance is a function of thickness. Nickel plating has a low coeffecient of thermal expansion - is magnetic. All steel parts having a hardness of Rc-40 or greater require a post bake at 375° + 25°F for 3 hour
Class 1: for decorative application on steel,zinc, copper.
Class 2: For engineering applications
Grade A: .0016" Thick
Grade B: .0012" Thick
Grade C: .0008" Thick
Grade D: .0008" Thick
Grade E: .0006" Thick
Grade F: .0004" Thick
Grade G: .0002" Thick
Electroless Nickel Plating Services to MIL-C-26074
Class I: As plated no subsequent heat treatment (a bake for hydrogen embrittlement
relief is not considered heat treatment).
Class II: Heat-treated to obtain required hardness. May be used on all metals not affected by
heating to 500F and above.
Class III: Aluminum alloys nonheat-treatable, and beryllium alloys processed to improve adhesion of the nickel deposit. Coated nonheat-treatable aluminum parts shall be heated for 1 to 1.5 hours at 375°F +/- 15°F to improve adhesion of nickel deposit.
Class IV: Aluminum alloys, heat-treatable, processed to improve adhesion of the nickel deposit. Coated heat-treatable aluminum alloys shall be heated between 240°F to 260°F for 1 to 1.5 hours to improve adhesion of nickel deposit .
Electroless Nickel Plating Services to ASTM B733-04
Type I: No requirement of phosphorous
Type II: 1-3% phosphorous (low phosphorous)
Type III: 2-4% phosphorous (low phosphorous)
Type IV: 5-9% phosphorous (medium phosphorous)
Type V: 10% or greater phosphorous (high phosphorous)
Class 1: As-deposited, no heat treatment.
Class 2: Heat treatment at 260 to 400°C (500-752°F) to produce a minimum hardness of 850 HK100.
Class 3: Heat treatment at 180 to 200°C (356-392°F) for 2 to 4-hr to improve coating adhesion on steel and to provide for hydrogen embrittlement relief.
Class 4: Heat treatment at 120 to 130°C (248-266°F) for at least 1-hr to increase adhesion of heat-treatable (age-hardened) aluminum alloys (such as 7075) and carburized steel.
Class 5: Heat treatment at 140 to 150°C (284-302°F) for at least 1-hr to improve coating adhesion for aluminum, non-age-hardened aluminum alloys, copper, copper alloys and beryllium.
Class 6: Heat treatment at 300 to 320°C (572-608°F) for at least 1-hr to improve coating adhesion for titanium alloys
Electroless Nickel Plate Services – AMS 2404
Class 1: Except for hydrogen embrittlement relief, no post plating thermal treatment.
Class 2: Thermal treatment at 450°F (232°C) or above to harden the deposit.
Class 3: Thermal treatment at 375°F (191°C) to improve adhesion for nonheat-treatable aluminum alloys and beryllium alloys.
Class 4: Thermal treatment at 250°F (121°C) to improve adhesion for heat-treatable