The Dacrotized metal surface treatment, with anticorrosion properties exceeding electrogalvanization Elecut, a bolt product with excellent corrosion resistance and insulation properties


DACROTIZED treatment developed Diamond Shamrock gives (anticorrosive film having both self-restoring function and sacrificial corrosion preventive function) to metal products, of which performance is superior to that of galvanizing. Owing to its excellent anticorrosive performance, it is used widely in various automotive parts,electric household appliances,building and civil engineering materials,etc. Low torque coefficient type is also available upon request.

Performance table

iItems Test method Test result
Salt spray test JIS Z 2371 1,000 hours
Torque coefficient Standards JIS B 1186 0.2〜0.3※1
※1:By doing additional surface treatment, low torque coefficient type is also available.

Treating process


By basket type dip-spin coating method, a film of excellent throwing power is formed.


Applications and Available sizes

ねじアイコンApplicable parts

Automotive parts,electric household appliances, building and civil engineering parts.

ねじアイコンCoatable materials Carbon steel of all grades, structural alloy steel
ねじアイコンsize nominal diameterr : 8mm or morestandard maximum dimensions : W500×L600×H100standard maximum weight : 30kg per itemsize other than the above size, please cotact to us.


In high voltage atmosphere,products having high insulating performance are needed. Takenaka have succeeded in development of bolts having high insulation and high corrosion resistance by combination of various anticorrosive bolts and insulating materials (insulation sleeve and insulation washer). Anticorrosive bolts are selectable from TAKECOATⓇ-1000, TAKECOATⓇ-CERAMIC1,and DACROTIZED depending on the required anticorrosive performance. Applicable to all materials, including double-ended bolts and hexagon bolts.

Performance table


●Dimension of insulation washer

d d2 d3 t
M12 φ24 φ13 4
M16 φ30 φ17 4
M20 φ37 φ21 4
M22 φ39 φ23 6
M24 φ44 φ25 6
M30 φ56 φ31 6


  • Dimension of L differs according to the type of flange or combination.
  • Bolt shape can be selected from double-ended bolt and hexagon bolt.
  • Consult us for other size(e.g. over M30 and inch thread).
  • Hexagon nut conforms to attachment to JIS B 1181 and steel washer conforms to bright round and plain round type of JIS B 1256.

●Characteristic of insulation sleeve and insulation washer

Insulation Tube Insulation washer
Material Fluorocarbon polymer Silicone rubber Ethylene-propylene rubber FRP
Volume resistance(Ω・cm) 1018 or more 2×1015 or more 2×1015 or more 1011〜1015
Dielectric strength(kV/mm) 40 25 25 10 or more
Dielectric constant 2.1 or less 3.2 3.3 3.5〜4.5
Compression strength(MPa) - - - 295~519
Standard color Transparent Light gray Black -
Standard thickness(mm) 0.5 1.0 0.5 4 or 6