To know the solution, it is important to first understand the problem. Why is corrosion happening, how do we stop it or slow it down, and what makes one product perform better then the other. Did you calculate in the human error factor?
- 3 Elements needed to get corrosion, similar to a battery, are
- a conductive medium such as moisture
- Why do coatings typically perform better over blasted vs power tool cleaned susbtrates
- Because power tool cleaning is often not carried out as diligently as blasting
- Corroded substrates can be very porous, preventing good wetting of the substrate…leaving microscopic air gaps allowing corrosion to continue, despite slower
- Corrosion residue under the coating remains active, and continues to expand. Especially non-flexible coatings tend to crack allowing moisture to penetrate
- Why do coatings applied on board often fail prematurely, even in first 1-3 years of application?
Weather conditions are seldom perfect, and often very challenging during voyage. Most coating technologies have limited tolerance to humidity, temperature, salt & chlorides on the substrate, and limited surface tolerance. If not applied within the tolerance of the product, the performance can reduce by up to 95%
If the humidity is high and/or substrate is not 100% dry (within dew point), the substrate will not be wetted properly, and barrier performace preventing the elements of corrosion will not exist or only limited.
Multi pack coatings require accurate mixing ratio. This is seldom measured in practice. Wrong mixing ratio or not respecting pot life will reduce performance significantly.
Most coatings used have low flexibility or limited elongation. Knowing that corrosion products under the coating will continue to expand, inevitably will result in coatings to crack, and corrosion to continue.
- How to stop or slow down corrosion?
- Blocking one of 3 elements by i.e. a barrier coating
- Have a less noble metal sacrifice itself – sacrificial anode
- Or a combination of the one or more of the above
- Knowing all this, what kind of coating technology should you be looking for to reduce on board maintenance life cycle cost?
- A coating that has high tolerance to challenging weather conditions, including high humidity, cold climate and/or damp substrates.
- Preferably a single pack coating
- A coating technology that has high elongation capability
- A breathable coating that allows for moisture vapour to travel through without blistering, still forming a barrier to the larger moisture molecule.
- A coating that tolerates application to damp substrates, still providing good wetting of the substrate, and penetration in microscopic porosities
So why Steelpaint Moisture Cure PolyUrethane (SP-MCPU)?
For more than three decades, Steelpaint has decisively enhanced the life and durability of heavy-industry facilities, particularly in maritime service and in shipping and offshore environments. Thanks to one-component polyurethane resins, our special high-tech Steelpaint coatings have raised the technological bar in corrosion resistance, offering impressive benefits over conventional epoxy coatings.
SP-MCPU – allround protection
Year after year, millions are lost as assets succumb to corrosion. Long-term protection of valuable investments calls for long-term protection of facility surfaces. Thanks to its unparalleled long-lasting performance, SP-MCPU is increasingly the coating of choice, winning out over conventional epoxy-resin systems. When it comes to battling aggressive industrial gases, mechanical stress, abrasion, salt water and the elements, SP-MCPU solutions offer standout performance in a wide array of application settings:
- Piers, sheet pilings, moorings, bridges, jetties, cranes
- Ships, offshore platforms, barrages, locks, ship hoists
- Pipelines, tanks
- Industrial facilities, power plants, refineries
Cure year-round? Even under the harshest conditions
Steelpaint coatings cure and protect right away, even under the most unusual circumstances:
- In marine environments and relative air humidity up to 98%.
- Unflagging resistance to a number of acids, chemicals, oils, fats and alkalines.
- Reliable application from -5°C up to +50°C.
- Long-life corrosion protection under the toughest conditions.
- Tried-and-tested compatibility with cathodic protection systems (certified by the Federal Waterways Engineering and Research Institute (BAW) Karlsruhe, Germany).
Time is money
No need to waste precious time on corrosion protection – just cure quickly and simply with SP-MCPU. Slash down-times and get the job done in a flash. Plus: reap the benefits of an intelligent combination of elasticity and hardness, minimizing transport and assembly damage to precoated parts. The advantages speak for themselves:
- Single component – for easy application and an end to mixing problems.
- Cures and penetrates quickly – for recoats in quick succession.
- Even when still wet, coatings are immediately environment-safe – resistance, for instance, to salt water.
- Superior adhesion to stubborn rust film, mechanically prepared steel surfaces and tenacious previous coats.
- Highly surface tolerant: In addition to normal blasting, UHP jetting, HP Jetting, Slurry blasting and manual surface preparation are possible
Comparison Stelpant vs. conventional material
- Only 1 component – so no mixing errors
- No-headache application in all environments, all year long – no matter the weather
- Easy application in relative air humidity up to 98%
- Tidal zones: entire system can be coated in 30 minutes incl. zinc primer – with immediate resistance to seawater
- Can be applied to slightly damp surfaces
- 1 component, so no waiting for reaction time
- No pot-life
- Long-life corrosion resistance – even when applied under harsh conditions
- Excellent adhesion of active zinc primer, even on mechanically or manually prepared surfaces and many old coats
- Slurry blasting, water jetting and manual surface preparation possible
- The SP-MCPU technology has high elongation and flexibility values, preventing microcracking when applied to expanding (well adhering) rust on the substrate
- 2 component – potential mixing errors
- Application depends on weather conditions and ambient temperatures
- No application in relative air humidity above 85%
- Tidal zones: generally only thick coats possible, without zinc primer. Danger of blistering
- Application to damp surfaces is not possible
- Dew point must be taken into account
- Reaction time only after components are mixed. Application time can be very limited – especially in extremely high temperatures
- Need to blast for best performance, poorly suited to water jetting
So success of onboard maintenance, and reduction of life cycle cost is very much depending on the tolerance of the coating system to the real world conditions of On Board Maintenance.
Various large shipowners have experienced the improved performance reducing life cycle costs, now using Stelpant PU Zinc as the preferred product for OBM.
Read also the article in the Scheepvaartkrant (Dutch) by clicking on following link.