ETP (Coil & Sheets)

ETP is a cold rolled mild steel coil or sheet, coated on both sides with tin by a continuous electrolytic operation, which when flow melted forms a tin iron layer in between the steel base and the lustrous free tin layer.


ETP may be of Single Reduced (SR) or Double Reduced (DR) type and available, both in sheet and / or coil form.

Single Reduced Electrolytic Tinplate (SR ETP)

SR ETP is produced by cold rolling of Hot Rolled Steel Coils followed by annealing and skin passing the annealed coil, before being coated with tin through an electrolytic process.

TCIL produces SR ETP in a wide range of thickness, temper grades and coatings (including differentially coated ETP) under BIS certification (IS 1993/ISO 11949) to cater to various end uses:

Edible oils

TCIL produces tinplate for fabrication of 15 kg / litre cans for packaging edible oils as per IS 10325, the specification for Square 15 kg / litre cans for Edible Oils, Fats, Vanaspati and Bakery Shortenings.

Paints

Electrolytic tinplate is the preferred packaging medium for paints. TCIL services the entire range of requirements for packaging of paint cans.

TCIL also caters to the conical pail requirements of the paint market & has now added tinplate for the drum segment of paint packaging to its product range.

Aerosol

Tinplate Aerosol cans are mostly made up of 3 components - a top cone containing the Valve opening, a body & a bottom dome. TCIL has the capability to service majority of the requirements for all components of Aerosol cans.

Battery Components

The key quality requirements for battery jackets & components are close tolerances on thickness and temper. While in the dry cell segment the small size battery predominates, the alkaline cell segment is also growing.

ETP required for producing all components - top, bottom & jackets - for dry cell / alkaline batteries are serviced by TCIL.

Processed foods

Open Top Sanitary Can (OTSC) Quality Tinplate conforming to IS 9396: Part 1 is required to be used for thermally processed foods.

OTSC tinplate is generally a differentially coated ETP, ideally suited for packaging processed food like mango pulp, gherkins, baked beans, pineapple rings, fruits and juices, mushroom, fish, meat, prawns etc.

TCIL is licensed to produce OTSC quality tinplate as per BIS Specification & markets OTSC certified to IS 9396: Part 1

Double Reduced Tinplate (DR ETP)

DR ETP is normally thinner but stronger than conventional SR ETP. DR ETP is produced by electrolytic coating of tin on a steel, which after an initial cold reduction and annealing is subjected to a second cold reduction with lubrication, which gives work hardening effect and imparts additional strength to Double Reduced material. TCIL produces DR ETP from 0.14 to 0.21 mm in DR08 (DR 550) grade.

Soft Double Reduced Electrolytic Tinplate (Soft DR ETP)

Soft DR ETP is Double Reduced material produced with lower second cold reduction as compared to the normal DR ETP with a hardness of 65+4/-3. Soft DR is available in thickness ranging from 0.18 to 0.23 mm. It has a brighter finish compared to SR ETP of the same thickness range & also offers a lighter option as compared to SR ETP in T65 temper grade.

Common features of SR ETP, DR ETP and Soft DR ETP

Passivation Film

3.5 – 6.5 mg/m2 of chromium per side (with 311 treatment) unless otherwise specified.

Oil Film

5 -12 mg. /sq. of DOS (total for both sides).

Mechanical Properties
Product Steel Grade/ Temper Designation Hardness HR 30T Scale
Single Reduced Electrolytic Tinplate (SR ETP) T 52 52 + 4/‒4
T 55 55 + 4/‒3
T 57 57 +4/‒3
T 61 61 +4/‒4
Double Reduced Electrolytic Tinplate (DR ETP) DR 550 (DR08) 73 +3/‒3
Soft Double Reduced Electrolytic Tinplate (Soft DR ETP) DR 480 65 +4/‒3
Surface finishes
For SR ETP Blackplate
Finish Surface roughness Ra Flow melted
Stone Stone 0.35 ‒ 0.60 Yes
Silver Matt ≥ 0.90 Yes
Matt Matt No

For DR ETP and Soft DR ETP, surface finish is available only in Stone Finish.

Coating Grades
Coating Code Nominal Coating Mass (gm/sqm) Min Avg Coating Weight (gm/sqm)
Per Surface Total Both Surface
Equally Coated E 1.12 / 1.12 1.12 2.24 1.8
E 2.8 / 2.8 2.80 5.60 4.9
E 5.6 / 5.6 5.60 11.20 10.5
E 8.4 / 8.4 8.40 16.80 15.7
Coating Code Heavily Coated Surface Lightly Coated Surface Heavily Coated Surface Lightly Coated Surface
Differentially Coated* D 5.6 /2.8 5.6 2.8 4.75 2.25
D 8.4 / 2.8 8.4 2.8 7.85 2.25
D 8.4 / 5.6 8.4 5.6 7.85 4.75
D 11.2 / 5.6 11.2 5.6 10.10 4.75

* Other combinations of differentially coated tinplate through mutual agreement with buyer

Marking System

As per BIS specification (IS 1993/ISO 11949) the marking system for differentially coated electrolytic tinplate consists of parallel lines about one mm wide, the distance between the lines indicating the coating masses. Coating-wise line spacing given on Tinplate sheets is given below:

Code Line Spacing
D 5.6/2.8 12.5
D 8.4/2.8 25
D 8.4/5.6 25 alternating with 12.5
D 11.2/5.6 37.5 alternating with 12.5

Alternately, heavier coated surface is marked with parallel lines spread 75mm apart

Special Properties of OTSC quality Tinplate

Iron Solution Value (ISV): 20 micrograms max; Tin Grain Size (TGS): ASTM 9 or less numerically.

These properties are guaranteed on the heavier coated side (8.4gm/m2 & above) only.