APC Article Reprints

MarineLine® coatings are viable option for veg oils
AS SEEN IN : Tanker Shipping & Trade


Advanced Polymer Coatings, manufacturer of MarineLine®, claims that a new report it has commissioned shows that for carriage of vegetable and edible oils, its system outperforms phenolic epoxy and zinc silicate products

Marinspec Associates' assessment of those surfaces posing the least threat to vegetable oils

Independent research shows chemical and product tanker operators who want to carry vegetable and edible oils have a viable alternative to stainless steel tanks or other coatings currently at the market, says Advanced Polymer Coatings (APC), the US headquartered manufacturer of MarineLine® 784.

In 2008, UK-based independent testing laboratory, Marinspec Associates (MA), investigated the influence of tank cleaning on the transmission of chemical cargoes retained in organic cargo tank coatings into vegetable oil cargoes. Its report concluded that the coating/material that performed the best (transmitted the lowest concentration of the chemical cargoes into the vegetable oils) was MarineLine® 784 produced by Advanced Polymer Coatings.

Based on these results, APC asked that MA conduct further testing, with the primary objective to compare the transmission characteristics of MarineLine® 784 against a typical zinc silicate coating, a typical epoxy phenolic coating, and stainless steel, under the International industry rules for the carriage of edible oils at sea. These coatings/materials were chosen since they represent the range of possibilities available to owners and charterers for carrying vegetable and edible oils in chemical and product tankers.

MA sought to investigate the cargo absorption (and retention) characteristics of these different surfaces under the same operational conditions, with a view to comparing the contamination threat each surface may pose, after exposure to styrene monomer (SM) and ethylene dichloride (EDC), to subsequently loaded ambient temperature and high melting point vegetable oils.

In this new test for APC, the following surfaces were evaluated:

  • mild steel coated with industry standard ethyl zinc silicate
  • mild steel coated with an industry standard epoxy phenolic
  • mild steel coated with MarineLine® 784
  • stainless steel, grade 304.

MA used the same exact methodology as in the previous project (Marin 02/08 – Federation of Oils, Seeds, & Fast Association — FOFSA International) consisting of 28 sample panels, with dimensions 125mm x 50mm x 3mm of each surface. These panels were pre-treated or post cured as follows:

  • ethyl zinc silicate coating: the panels were washed in fresh water at 25ºC, dried, washed in toluene and then dried again
  • epoxy phenolic coating: panels were post cured in accordance with the manufacturer’s published requirements
  • stainless steel grade 304: panels were washed in toluene and dried, before being passivated in accordance with ASTM A380
  • MarineLine® 784: panels were washed in fresh water at 25ºC and dried. No further post curing was necessary as the panels used in this project were those that had been previously post cured and used in the initial project in 2008.
    Triplicate panels of each surface type were exposed either to SM or EDC for a period of 30 days at 30ºC, before being removed from the chemicals and cleaned by one of the following specified cleaning regimes
  • ‘cold’ washing procedure with one hour cold seawater recirculation, cold fresh water flush, and natural ventilation for approximately 24 hours
  • ‘Hot’ washing procedure with one hour cold seawater recirculation, 4 hours hot (60°C) seawater recirculation, two hours steaming (maximum temperature 55°C), and natural ventilation for approximately 24 hours.
    After cleaning, the test panels were individually, fully immersed in the following vegetable oils:
  • crude sunflower oil (CSFO) at 30°C
  • refined and bleached deodorised palm stearin (PS) at 70°C.

The panels remained in the vegetable oil for 30 days in order to maximise the transmission of any retained chemical cargoes into the vegetable oils. After this time, all the panels were removed and each individual sample of oil was analysed for the presence of the respective chemical cargoes by gas chromatography mass spectrometry (GC/MS) at an independent certified public analyst’s laboratory.

The analytical results, as reported by MA, quantifies the transmission of SM and EDC into CSFO and PS after the ‘cold’ and ‘hot’ tank cleaning operations. It should be noted that these results are the average of the individual triplicate results that were corrected to take into consideration a contact ratio of 1m² of coating to1m³ of vegetable oil cargo. This is the same correction used and reported in Marin 02/08  testing, and is considered to be typical of the surface-area-to-volume ratio which may exist on an IMO type II/III chemical tanker.

All of the subject surfaces are commonly used in the cargo area of chemical tankers and, as such, all have the potential to come into contact with any combination of different chemical cargoes and/or vegetable oils.
MA’s observations were that the surfaces posing the least threat to the vegetable oils were stainless steel 304, industry standard zinc silicate and MarineLine®. However, the stainless steel used in this project was new stainless steel which had been degreased and fully passivated prior to exposure to the chemical cargoes. Similarly, the zinc silicate used was a newly applied coating, which was washed in fresh water, dried, washed in clean toluene, and dried again, prior to exposure to the chemical cargoes.

As such, these two surfaces can be considered to be in ‘new’ condition. Had these two surfaces been in a ‘used’ condition, their performance may have been different, according to the report.

MarineLine® performed in much the same way as previously reported with the laboratory results for styrene monomer being consistently below the detection limit (2mg/kg) of the analytical equipment. The laboratory results showed very slight traces of EDC in the vegetable oil samples which were exposed to the panels and which had been washed in the ‘cold’ washing procedure.

It should be noted that the panels which were ‘hot’ washed, did not show any traces of EDC in the vegetable oil samples but even so, after the results were adjusted to a surface-area-to-volume contact ratio of 1:1, they were equivalent to a contamination threat of less than 0.30 mg/kg.
Importantly, the surface posing by far the greatest threat was the industry standard epoxy phenolic coating. The results for transmission of both chemical cargoes showed very similar trends to those reported in the Marin 02/08 report, reaching a maximum of 25.1 mg/kg for styrene monomer and 45.0 mg/kg for EDC.

According to Donald J. Keehan, chairman of Advanced Polymer Coatings, “These tests clearly show evidence that MarineLine® performs as well as stainless steel in ensuring edible oil purity, when tested respectively with styrene monomer and EDC as last immediate cargoes. MarineLine® also totally outperforms phenolic epoxy and zinc silicate coatings in these applications.

“This opens up a whole new market for chemical and product tanker operators who want to carry vegetable oils and edible oils with MarineLine®-coated cargo tanks, without having to use stainless steel tanks or other coatings.