MacDermid have updated the finish protoc

MacDermid have updated the finish protocol for ZinKlad 250 – Ford S437. From April 2013, Torque ‘N’ Tension 08 and 15 will be the preferred topcoats. Additionally ZinKlad 96 is now added as S437U for zinc plated and trivalent passivated finishes without a topcoat.


Ford – Change to the WSS-M21P17 specific

Ford – Change to the WSS-M21P17 specification
Ford has authorized MacDermid to communicate changes to the S437 (ZinKlad 250) range of zinc electroplated fastener finishes. The current WSS-M21P17 will move to the new specification WSS-M21P52. The major changes involve cyclical corrosion testing and a change to some of their torque-tension requirements.

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Coatings for high tensile fasteners

Mechanical plating

High tensile fasteners are mechanically plated

When coating performance is considered, hours to white or red rust are the normal criteria. However with high tensile fasteners, threaded or unthreaded, being free of hydrogen embrittlement is an equally important factor. For this reason components such as rivets and safety critical fasteners are zinc coated using a mechanically applied process rather than traditional electroplate. This process also offers advantages in bulk application against organic dip spin that even the smallest fastener can be treated without head / recess fill or parts sticking together.

Mechanical plating

 In the mechanical plating process the zinc is present as fine dust. It is deposited by a cold welding process. Impact energy is transferred from a rotating open ended barrel through glass beads to the zinc dust. This impacts the zinc against the steel substrate. The resulting deposit provides corrosion protection to the articles without introducing hydrogen embrittlement into the part.

The main features of the mechanical zinc process can be summarised as:

• No risk of Hydrogen Embrittlement
• Excellent corrosion protection
• Choice of zinc, zinc aluminium or zinc tin alloys
• Automated bulk process
• Room temperature, cold welding batch by batch capability
• Non-electrolytic process
• Thicknesses can range from 8µm to over 75µm

The benefits to the specifier are reliability, security and value.


 The consistency of mechanical plating can be demonstrated by the replication in processing and the resultant coating. Additionally mechanical plating is specified by automotive manufacturers within the ZinKlad approved applicator program.

Plating process

The plating process is defined by process steps which are always the same. The only change, batch to batch, is the amount of material added (i.e. zinc dust). These quantities are correlated to the surface area being coated and the thickness required. These factors mean that the results are reproducible time and time again.

Coating performance

250 hours neutral salt spray

Protects for more than 250 hours in neutral salt spray

This reproducibility means a predictable coating is produced. Mechanical zinc plating, specified for over 30 years now by many major automotive manufacturers, delivers corrosion resistance similar to electroplated zinc for the same given zinc thickness. This means that an 8µm coating will resist more than 250 hours to red rust. Therefore exceeding requirements for:

• Non threaded fasteners such as rivets for joining metal
• Threaded fasteners used in safety critical assemblies such as seat belt mountings

Applicator program

Automotive companies often specify their surface finishing within an applicator program. This program aids coating reliability through a common audited standard. This helps to ensure the same coating performance throughout the applicator base, regardless of geographical applicator location.


A common feature of the 2 component types mentioned above is that both are constructed from high tensile steel. It is generally accepted that steels having a hardness above Rockwell C-40 are susceptible to hydrogen embrittlement.

One of the issues of hydrogen embrittlement, is that the higher-strength steels which are used to bear high loads are the very steels which can fail from hydrogen embrittlement at loads much less than their design load. The role which the hydrogen plays in the failure mechanism includes factors such as internal pressure from gas formation, formation of metal hydrides, stress concentration due to interactions with metal imperfections, and micropore or microcrack formation.

This now returns to the need for a coating free of hydrogen embrittlement to prevent failure in use. For the components mentioned above, hydrogen embrittlement could mean:

• A Rivet which fails to pierce and join metal layers
• A safety critical bolt which fails under intense load


Rivets in pile

High tensile self piercing rivets are also plated with mechical zinc alloys

Mechanical plating is an economical method of producing zinc coatings on high tensile steels due to:• No need for the hydrogen de-embrittlement process – Electroplated zinc coatings need to be de-embrittled within 2 hours of plating at 200ºC for 4 – 24 hours (dependant on part geometry and packing density). Additionally any passivation must be applied following this baking operation. These steps add cost due to increased process stages and energy consumption.

 • Automated equipment for bulk processing – Mechanical plating is applied in bulk processing, often in automated equipment. This increases productivity due to high loading and reduces operator costs.

• Coating uniformity and freedom from parts ‘sticking’ – These factors can reduce costs when compared to organic dip spin finishes, especially on rivets or fasteners with recessed heads.

• Low environmental impact – Finally the mechanical process results in very little waste material. This is because the majority of the material added during the plating operation is consumed to produce the final deposit.


Mechanical plating, extensively specified for over 30 years now, is considered one of the 3 primary coating systems for threaded and non-threaded fasteners. Primarily specified to provide sacrificial protection to high tensile steel components, it offers advantages in its ability to treat small and recessed parts without sticking or filling issues. The coating is uniform and consistent and can be specified for both joining and safety critical applications. Finally the bulk nature and low waste make mechanically plated sacrificial coatings extremely cost effective.

ZinKlad moves into India

  ZinKlad Plated Bolts

LPS  and Sundram become ZinKlad Approved Applicators

MacDermid India are very pleased to add LPS (Rohtak) and Sundram Fasteners (Krishnapuram) to our list of ZinKlad Approved Applicators (ZAPs). The approval of these new ZAPs reflects the growing importance of surface finishing to global automotive standards in india market.

India fastener market      India flag

The majority of fasteners in India today are consumed by the developing automotive sector. With global OEM’s such as Ford, Honda and Hyundai  now manufacturing vehicles for both domestic and export sales, the use of hexavalent chromium free passivates is becoming an important factor in this supply chain.


Lakshmi Precision Screws Ltd, established in 1972, provides high tensile fastening technology globally. having Joint Ventures, License Agreements, and Alliances with different fastening companies worldwide.  The Company is located in Rohtak (Haryana) just sixty kilometers from New Delhi.

Bolts plated in ZinKlad 1000

LPS offer ZinKlad 250 and ZinKlad 1000

Recently LPS has established two operating units, one in Rohtak and another in Industrial Modal Town, Manesar. Collectively all the four units have a total production capacity of 25,000 metric tons (MT) per annum.

LPS also caters to the needs of  wind energy, oil & gas, locomotives, agriculture equipment and machine building industries.

Sundram Fasteners

ZinKlad 250 plating

Sundram offer ZinKlad 250 finish

Part of the US based TVS Group and headquartered in Chennai, Sundram Fasteners has become a supplier of choice to leading customers in the automotive and industrial segments worldwide.

Over the years, the Company has acquired cutting-edge technological competencies in forging, metal forming, close-tolerance machining, heat treatment, surface finishing and assembly. Manufacturing locations are supported by engineering and design personnel working on new product design and development.

The product range consists of high-tensile fasteners, powder metal components, cold extruded parts, hot forged components, radiator caps, automotive pumps, gear shifters, gears and couplings, hubs and shafts, tappets and iron powder.

ZinKladZinKlad logo

Launched 10 years ago to help automotive engineers specify the right products to meet End of Life Vehicle requirements it has enabled many global OEM’s to specify higher standards than they had previously achieved.

Today ZinKlad represents not only the best method for achieving hexavalent chromium free performance coatings, but also:

  • Approved applicators: Applying these products to a common audited standard ensures the same coating performance throughout the applicator base.
  • High performance: Exceeding corrosion resistance of hexavalent chromate systems and exceptionally consistent torque and tension characteristics.
  • Global consistency: Wherever ZinKlad coatings are applied, applicators know they are using the same high performance products.

Of course, compliance with legislation, such as ELV & RoHS, and predictable torque-tension performance continue to be essential requirements. ZinKlad continues to deliver on all of these needs.

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