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3LPP anticorrosive three layer polypropylene coating conforming to DIN 30678:2013

This anti-corrosion coating consists of the following layers:

epoxide layer of minimal thickness of 60 µm,
polypropylene copolymer layer of minimal thickness of 140 µm,
polypropylene layer of minimal thickness between 1.8 and 2.5 mm.

Izostal S.A. manufactures coated steel pipes of diameter between 21,3 and 1220 mm and length between 8 and 18 linear metres; moreover we provide coating services with reference to pipes delivered by our customers.

Coating process may be divided into the following stages:

grit blasting of the steel pipe surface to Sa 2 1/2 in line with PN-EN ISO 8501-1:2008,
induction heating of the pipe up to 180-200°C,
electrostatic spraying of epoxy powder on preheated pipes,
electrostatic spraying of polyethylene or polypropylene copolymer powder,
ring extrusion of polyethylene or polypropylene sleeve,
coating cooling with water,
machining of the pipe ends,
temporary rustproofing of pipe ends with anticorrosive lacquer.

Typical features of the three layer anticorrosive coating applied on steel pipes include the following:

high resistance to mechanical damage,
resistance to chemical substances, moisture, breakdown, high temperature and UV radiation,
good adhesion of the coating to steel pipe surface,
anticorrosive protection of underground pipelines for approximately 50 years,
complete protection of steel pipe welds,
easy connection of coated pipes without damaging the coating,
the coating is neutral to the natural environment.

Steel pipes coated with 3LPP coating are used in line with the ZN-G-3910 standard “High pressure gas mains subject to special tests" for directional drilling through obstacles.
Polypropylene is a perfect material, displaying high mechanical and thermal resistance.

Polypropylene hardness reaches 64 points in the Shore “D” scale, which is more than polyethylene. Moreover, polypropylene yielded higher results in the case of destructive tests carried out in low temperatures (in comparison to polyethylene), e.g. resistance to the environmental stress corrosion – ESCR (>3000 h for polypropylene and > 1000 h for polyethylene).

Polypropylene is resistant to UV radiation (contains UV stabilisers) and displays high thermal resistance as it is intended to be used in high temperatures (polyethylene in max. 60° C and 80°, whereas polypropylene operation temperature reaches 100°C and 110°C).

3LPP coating protects steel pipes efficiently against mechanical damage.

Polypropylene coating meets requirements resulting from technical terms applicable in construction of gas mains; so far steel pipes coated with a reinforced three layer polyethylene coating with an additional laminate cover have been used in the case of directional drilling through obstacles.

3LPP coating displays extremely good performance in the following areas:

adhesion of to steel pipe surface,
resistance to impacts,
resistance to abrasion,
resistance to penetration force,
hardness and stiffness,
unit grounding resistance of the gas main.

3LPP anticorrosive three layer coating conforming to DIN 30678:2013

Test type	Test conditions	Test results
Test type	Test conditions	Actual	Required by the standard
Coating thickness	Ambient temperature	> min. required in line with DIN 30678	In line with DIN 30678, depending on the pipe diameter
Coating tightness	Ambient temperature	No breakdown at U=25kV	No breakdown at U=25kV
Adhesion of the coating to steel pipe surface	T = (50±5)°C T = (90±5)0C	200-400N/cm 150-270N/cm	min. 100N/cm min. 80N/cm
Coating resistance to impact	T = (23±2)°C	No breakdown at U=25kV	No breakdown at U=25kV
Coating resistance to penetration	T = (90±5)°C	0,18-0,20 mm	max. 0,3 mm
Coating unit elongation at break	T = (23±2)°C	900%	min. 300%
Coating unit resistance	T = (23±2)°C t = 100 days	≥10⁸Ωm²	Rs ≥10⁸Ωm²