Effects of graphene on the corrosion of epoxy zinc-containing coatings

A recent report described the effect of graphene on the corrosion of zinc particles in waterborne epoxy zinc-containing coatings. In the study, graphene/ waterborne epoxy zinc-containing coatings with different graphene contents were prepared, and their corrosion resistance properties were investigated by electrochemical impedance spectroscopy (EIS), immersion testing and neutral salt spray.

The results showed that addition of 0.6 wt% graphene into the coating could remarkably improve its cathodic protection and barrier performance compared to the coating without graphene.

In addition, the effects of graphene on the corrosion evolution of zinc particles in the coating were studied by the field-emission scanning electron microscopy (FE-SEM) coupled with energy dispersive spectroscopy (EDS), which showed that the zinc particles near the interface between a steel substrate and the coating corroded first after the corrosive media diffused into the coating. The zinc particles then continued to be corroded from the interface to upper part of the coating as they provided cathodic protection to the substrate due to the electrical connection of graphene. X-ray diffraction (XRD) patterns confirmed the corrosion products of the zinc particles were mainly consisted of Zn5(OH)8Cl2.H2O.

The study was published in Progress in Organic Coatings, Volume 140, March 2020.

Passive Fire Protection – The Financial Cost of Getting It Wrong

Passive Fire Protection – The Financial Cost of Getting It Wrong

There is change afoot in the world of passive fire protection (PFP), especially in the protection of structures in high-risk industries such as oil and gas. Unlike in many other sectors, it is the industry itself that is leading the way in more stringent competencies in application and inspection of PFP to ensure quality installations.

What are the forces that are driving this change? In this article, the first in a six-part series we’ll be publishing over the coming weeks, we look at the financial cost of getting passive fire protection application wrong.

What is passive fire protection?

PFP systems reduce the rate at which temperature rises on the protected structure. They do this primarily through heat absorption, reflection and insulation. They are passive because they don’t require external activation to work, such as water deluge, which is why they are considered more reliable, provided they are installed correctly.

In high-risk facilities such as offshore oil and gas installations, the most common form of PFP is epoxy intumescent coatings. These protect structural steel from extreme heat and provide full corrosion protection. They work by swelling and producing a carbonaceous char when heated, which insulates the steel substrate.

How are PFP coatings applied?

Epoxy intumescent coatings are usually applied by spray application using dedicated spray pumps. They must be applied onto properly prepared surfaces, and surface preparation and priming are critical to their adhesion and, in consequence, longevity. Epoxy PFP systems are frequently reinforced with a fibre mesh system, the primary purpose of which is to reinforce the char formed in a fire situation. On occasion they might be reinforced with a wire mesh, but in some systems there is no reinforcement. Typically, the thickness of an epoxy intumescent coating is between 3mm and 20mm.

The significant advantage of epoxy PFP coatings is their toughness and durability, meaning that they can be applied to steel before it is erected. In modular construction they have the ability to withstand the steel deformation when modules are loaded for transportation to their installation site and during the offloading and installation process.

PFP is failing – but why?

The international standards for PFP have been improved tremendously over the last few decades, especially in response to headline disasters like Piper Alpha and more recent incidents. However, in recent years the industry has witnessed a marked increase in the failure of PFP before the plant is commissioned. The reason for this appears to be changing market dynamics. Let us explain.

There used to be only very few manufacturers that produced epoxy PFP intumescent coatings. It was a highly specialised field, and consequently the margins were high. These manufacturers would provide free-of-charge on-site technical service personnel to help ensure correct application of PFP.

Over the years an increasing number of manufacturers have entered the epoxy intumescent market, chasing the same market opportunity. Consequently, margins have been reduced and a level of commoditisation has taken place. Additionally, the drive in the oil and gas industry to reduce project costs has exerted considerable pressure in all areas of construction and supply. The result has been an inability for manufacturers to offer the same level of on-site technical services that was previously provided free of charge, and instead fabricators and contractors are charged for these services. There is no doubt that this has resulted in a reduction in available competency to ensure quality installations.

A further factor is the tendency to treat epoxy intumescent coatings like paint and even to call them ‘paint’. Whilst they are similar, especially the epoxy types, there are significant differences requiring specific skills and understanding for quality PFP installations.

Shortage of early-stage technical competency is a false economy

PFP is an expensive necessity, and from a financial point of view keeping a lid on those costs is important. However, the cost of correcting poorly applied PFP is colossal. When a PFP system is incorrectly installed or fails, the impact can include:

  • Risk to the project schedule and potential delay of production due to lack of authority to operate whilst corrective action is taken
  • The high cost of access, including scaffolding, to carry out remedial work, particularly in the offshore environment
  • Impact on other trades whilst areas are ‘quarantined’ for corrective PFP work to be carried out
  • The sheer difficulty of removing and reinstating in an on-site environment

Experience from a leading coatings manufacturer shows that:

Offshore maintenance is 15 to 20 times more expensive than performing work at a yard, and corrosion accounts for 60% of offshore maintenance costs. Further, 85% of coating failures appear within 1 to 3 years, with 95% of failures occurring because of:

  • Incorrect specification choice
  • Poor surface preparation
  • Poor application
  • Climatic conditions

To put this into perspective, PFP that is commissioned at an implementation cost of, say, $10 million for a facility in an isolated area of the world (the best fields are usually isolated, right?) and is poorly implemented could cost $150 million to $200 million in rectification costs.

From a purely financial viewpoint, it’s clear that if you spend money upfront you save hugely on project overrun costs, let alone the project complexity of re-work.

How the industry is evolving

The industry is calling for improved competency in the application and inspection of PFP. It simply cannot continue to burn cash on rectification requirements that could and should be avoided. Whilst development, testing and certification for use of PFP materials is regulated, the application and inspection of PFP is not regulated in the same way.

Currently, owner operators specify that inspectors should be paint level 2 qualified as a minimum. What this means is that someone who has good knowledge of paint, but no knowledge or experience of PFP, can go onto a site and inspect PFP. As manufacturers continue to bring new and improved products to the market, with additional features and benefits, this issue is magnified.

In response to this and other issues, PFPNet was established around four years ago to tackle what was becoming a significant loss of skill in the industry across a broad range of PFP topics. With an objective to improve knowledge and understanding, and increase competency across the hydrocarbon passive fire protection industry, PFPNet – whose membership comprises owners, engineers, contractors, manufacturers, and others – has tapped into the skills of its members to tackle key subjects including improving quality of installation.

As PFPNet has evolved and grown with a broad range of membership of companies and individuals who truly understand the business, it has become clear that there is a real desire to develop best practice, navigate regulations, and remove confusion and conflicts.

The result is the evolution of a new PFPNet Competency Framework, which will lay out the knowledge and competency levels expected across all disciplines in the fireproofing of industrial facilities. It is expected that this framework will be mandated by owners and other stakeholders as a requirement for projects and operations.

To stay in the know and be part of the PFP conversation, contact either John Dunk at PFPNet or David Mobbs at ICorr.

Enhanced corrosion resistance and weathering resistance of waterborne epoxy coatings

This new study focused on the enhanced corrosion resistance and weathering resistance of waterborne epoxy coatings with polyetheramine-functionalised graphene oxide. Polyetheramine (D230), an epoxy curing agent, was grafted on graphene oxide (GO) surfaces, which can be stably dispersed in a waterborne curing agent for more than 8 months. Waterborne epoxy coatings reinforced by D230-functionalised GO (DGO) were applied on carbon steel surfaces.

According to the electrochemical impedance spectra, the impedance modulus at 0.1 Hz remained at 2.2 × 109 Ω after 150 days of immersion in 3.5% NaCl with a 0.2 wt% DGO-reinforced waterborne epoxy coatings, whilst that of the neat epoxy coating dropped below 1 × 107 Ω after 10 days. In addition, the addition of DGO was found to enhance the weathering resistance of waterborne epoxy coatings. After 60 days of the UV aging test, the yellow colour index of a neat epoxy coating was 1.6 times that of a 0.5 wt% DGO/epoxy coating. The residual pencil hardness of the 0.5 wt% DGO/epoxy coating was three levels higher than that of neat epoxy coating.

The study was published in the Journal of Coatings Technology and Research, Volume 17 (2020).

Latest Literature – Abrasion resistance of coatings for hydraulic structures

A report has been published recently comparing the abrasion resistance of conventional vinyl-based coating systems, polymer with polymer matrix composite coatings, fibrous polymer coatings, and ultrahigh molecular weight polyethylene (UHMWPE).

There is an increased demand for abrasive wear-resistant coatings that add durability to steel hydraulic structures, particularly for those subjected to flowing water with debris and alternate wet/dry cycles. These coating systems provide not only corrosion and chemical resistance, but also good erosion and abrasion resistance to the metallic surfaces, which are constantly exposed to flowing water containing sand particles and debris. Generally, vinyl-based coatings are used on hydraulic steel structures to protect them from corrosion and abrasion.

This new study, by U.S. Army Corps of Engineers, evaluated the abrasion of six coating systems using a reciprocating abrader under dry and wet conditions. The wettability of the coating systems and its effect on the wear rate under the presence of water was also studied. In addition, scanning electron microscopy of the wear tracks on different coatings was conducted to study and identify their failure mechanisms.

Based on the results, UHMWPE and polymer–ceramic composite coatings were found to perform significantly better than the conventional vinyl-based coatings.

The study was published in the Journal of Coatings Technology and Research, Volume 17 (2020).

2020 PDA Conference and Exhibition

2020 PDA Conference and Exhibition

PDA Europe is organising its Annual Conference and Exhibition on 17-18 November 2020 at the Crowne Plaza Hotel, Porto, Portugal

The applications of polyurea are widespread and the technology keeps on innovating and improving, and this event is a unique forum in Europe for all the stakeholders of Polyurea and has been designed to discuss and present all its facets.

This year, the event will take place over two days with the General Assembly taking place on the 17th. The two days are packed with presentations, interactive sessions, education courses, spray gun workshop, table top exhibition and networking moments. There are sponsorship and table top exhibition opportunities, and more details about the event can be found at, www.pda-europe.org