Rack Chrome Plating

Parts are hung on a hanger for electroplating,   with good uniformity of coating thickness and a wide controllable range   (5-50μm), suitable for complex shapes

Steel, copper alloys, zinc alloys

Large non-standard parts (large mechanical   parts, mold cavities, automobile chassis brackets), special-shaped parts   (such as valves, pipe fittings)

Large non-standard parts with high   requirements for coating uniformity and dimensional accuracy, such as   engineering machinery structural parts, precision molds, etc.

Barrel Chrome Plating

Small parts are placed in the drum for batch   electroplating, which is highly efficient and suitable for batch processing   of small parts. The coating thickness is relatively thin (2-15μm).

Steel (screws, washers), small copper parts

Small non-standard parts (such as precision   hardware, electronic connectors, fasteners, small special-shaped stamping   parts)

Anti-corrosion and wear-resistant treatment of   large quantities of small non-standard parts, such as electronic equipment   connectors, furniture hardware, etc.

Brush Chrome Plating

Local electroplating, use a plating pen to   touch the surface of the part to apply electroplating, targeted repair or   strengthening of the local area, the coating thickness is controllable   (1-20μm)

Steel, stainless steel, copper, aluminum   (pretreatment required)

Non-standard parts that require local repair   (such as shaft wear parts, local mold damage parts), and local reinforcement   parts of large parts

Local repair of non-standard parts (such as   repair of machine tool spindle wear), local strengthening of large parts that   cannot be electroplated as a whole

Trivalent Chrome   Plating

Using trivalent chromium salt as electrolyte,   it is environmentally friendly (toxicity is only 1/100 of hexavalent   chromium), and the coating has strong corrosion resistance.

Steel, zinc alloys, copper alloys

Non-standard parts with high environmental   protection requirements (such as food machinery parts, medical equipment   parts, and children's product parts)

Fields with strict environmental protection   standards, such as food processing equipment, medical equipment, toy parts,   etc.

Hexavalent Chrome   Plating

Traditional technology has high coating   hardness (800-1000HV) and excellent wear resistance, but it is highly toxic   and has strict environmental protection requirements.

Steel (primary), copper alloys

Non-standard parts with extremely high   requirements for wear resistance and decorativeness (such as mold cutting   edges, hydraulic rods, precision bearing sleeves, tool accessories)

Applications with extremely high requirements   for wear resistance and decorative properties and loose environmental   restrictions, such as industrial molds and heavy machinery hydraulic   components.

Hard Chrome Plating

The coating has a large thickness (20-100μm),   high hardness (800-1200HV), and strong wear resistance and corrosion   resistance

Medium- and high-carbon steel, alloy steel,   cast iron

Non-standard parts subject to friction and   wear (such as crankshafts, plungers, machine tool guides, and mold working   surfaces)

Non-standard parts subject to friction and   wear, such as engine crankshafts, injection molding machine screws, machine   tool slides, etc.

Decorative Chrome   Plating

The coating is thin (0.5-3μm), bright and   smooth, and has both decorative and anti-corrosion effects. It is often used   as a covering layer for the base layer (nickel).

Copper alloys, zinc alloys, steel (priming   required)

Non-standard parts with high appearance   requirements (such as instrument housings, decorative mechanical parts, and   bathroom accessories)

Non-standard parts with high requirements on   appearance, such as precision instrument housings, high-end furniture   decorations, bathroom hardware, etc.

Black Chrome Plating

The coating is black and has both decorative   and certain wear resistance; it is achieved by adjusting the composition of   the chrome plating solution (such as adding iron and cobalt salts), and the   thickness is 1~5μm.

Steel (priming required), copper alloys, zinc   alloys

Optical instrument parts (matt), weapon parts   (camouflage, anti-reflective), automotive interior parts (textured   decoration).

Parts with special requirements for appearance   color (black) and slight wear resistance.

Rack plating, barrel plating, and brush   plating: These are classified by the plating method, differing in the way the   part contacts the plating solution (hanging, rolling, or brushing).
  Trivalent chromium and hexavalent chromium plating: These are classified by   the valence state of the chromium ion, differing in the form of chromium in   the electrolyte (trivalent chromium salts or hexavalent chromium salts).
  Hard chromium and decorative chromium plating: These are classified by the   coating's function, differing in the coating's performance emphasis (hard   chromium emphasizes hardness and wear resistance, while decorative chromium   plating focuses on appearance and corrosion resistance).

Note: Direct chromium plating on non-ferrous   metals (such as aluminum and copper) has poor adhesion and requires a   pre-plated intermediate layer (e.g., nickel plating on aluminum and copper).
 
  Due to environmental restrictions, hexavalent chromium plating has been   gradually replaced by trivalent chromium in the EU and other regions.   However, hard chromium plating remains widely used due to its performance   advantages.
 
  For complex, non-standard parts (such as deep holes and blind vias),   optimized hangers and the addition of auxiliary anodes are required to ensure   uniform coating.

Applicable   substrates

Almost all metal materials can be chromium   plated, but it is difficult to plate chromium on steel with high carbon   content (C>0.90%), steel with high silicon content (Si>1.00%), steel   with high chromium and tungsten content, gray cast iron, ductile iron, magnesium,   and magnesium-containing aluminum. Steel castings can be chromium plated when   there is no metal debris or cracks on the surface.

Surface roughness of   substrate before chrome plating

The surface roughness should be consistent   with that after chrome plating. Generally, the surface with low requirements   is Ra0.8μm, and the sealing and rotating surface is Ry3.2μm.

Surface hardness of   substrate before chrome plating

Should be 40-60HRC. The hardness of   chrome-plated steel should not exceed 60HRC, and quenched steel should be   annealed at 180-200°C.

Coating appearance

The surface of the chrome plating is silvery   white with a slight bluish tint, has a metallic luster, and is free of   defects such as blistering, shedding, chrome nodules, pinholes, etc. The   surface should be flat, smooth, and uniform in color.

Coating hardness

Generally, it can reach 900-1000HV. The   hardness will decrease as the working temperature rises, such as 830HV at   100°C and 750HV at 150°C. The chrome plating hardness of the screw drill   rotor is 850-1000HV0.2

Coating thickness

The most economical diameter is about 30μm,   and it can reach 800μm when wear compensation is applied. The chrome-plated   diameter of the screw drill rotor is greater than 0.10mm at the large   diameter and greater than 0.04mm at the small diameter.

Corrosion resistance

Chrome plating of screw drill rotors   requires a 144-hour neutral salt spray test with a performance rating of   RP/RA≥9/9 vs B

Bond strength

There should be no separation, delamination   or falling off between the coating and the substrate. Testing can be carried   out according to the file test method or thermal shock test method in GB/T   5270.

Wear resistance

For example, if the rotor of a screw drill   is chrome-plated, the coating wear loss is less than 0.25g according to the   JB/T 7705 standard dry sand/rubber wheel abrasive wear test method.