Relevant information in alphabetical order

 Acid Value  Gas Free  Synonyms
 Cargo Conformity  IMO Categories  Tank Cleaning Chemicals
 Cargo Contamination  Inorganic Acids and Alkalis  Temperatures, storage/loading
 CAS Number  Methanol and Ethanol  Transport and Storage
 Coating Discolouration  Non-Aggressive Chemicals  Ventilation
 Curing  Repair Procedure  Zinc pick up 
 Edible & potable cargoes  Substrate and Curing  

The maximum acid value of a cargo for each coating system is detailed in Note 3 with the acid value being determined by the ISO 660 (1996) method.

For guidance only, the acid values determined by ISO 660 (1996) are related to the approximate weight percentage of free fatty acid as mentioned below:


Maximum acid value
(acc. to ISO 660-1996)

Approx. Percentage
Free Fatty Acid

 Sigma PhenGuard

 no limit

 up to 100 %

 Sigma NovaGuard


 30 - 50 %

 SigmaGuard 720 (Sigmaguard EHB)


 6 - 10 %

 SigmaGuard 750 (Sigma Silguard MC)


 1.5 - 2.5 %

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This resistance list is based on practical tests carried out on pure and/or commercial cargoes. The composition of many commercial cargoes contained in this resistance list are subject to change and therefore may vary in composition. PPG PMC has no control over the composition of these cargoes, their sequence or the conditions of service and expressly disclaim any responsibility for the results obtained from their use or for any incidental or consequential effects of any kind. Concentrations mentioned in this list have been expressed in weight percentage.

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Absorption of cargo by the coating may occur and subsequent desorbtion is dependant on factors such as temperature, ventilation, humidity, absorbed components, tank cleaning procedures etc. Contamination of cargo by the coating may occur but is usually limited to the first cargoes after application of the coating and should be taken into account for sensitive cargoes such as edible and potable cargoes and cargoes with a high purity such as fibre grade glycol. Such cargoes should be avoided in the early life of the coating system. Given the subjectivity of taint and taste, it is recommended that in case of storage / carriage the client first carries out testing of cured panels of the chosen coating in contact with the cargo in question to ensure suitability. Chemical reaction between cargoes may well result in the formation of products which may cause breakdown of the coating.

To avoid cargo contamination, care should be taken that any previous cargo retained in the coating is desorbed prior to loading of the next cargo and that effective tank cleaning procedures are used. PPG PMC does not accept any responsibility or liability in relation to cargo contamination whatsoever.

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CAS registry numbers are unique numerical identifiers for chemical compounds, polymers, biological sequences, mixtures and alloys. They are also referred to as CAS numbers, CAS RNs or CAS #s. Chemical Abstracts Service (CAS), a division of the American Chemical Society, assigns these identifiers to every chemical that has been described in the literature. The intention is to make database searches more convenient, as chemicals often have many names.
To enable better identification of the cargo to be transported/stored, CAS numbers can be found in the resistance list.

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Some products may cause surface discolouration of the coating, which is difficult to remove by tank cleaning operations, and subsequent cargo contamination is possible. Discolouration is normally a surface phenomenon and in itself does not necessarily constitute a defect. PPG PMC does not accept responsibility for coating discolouration and cannot be held liable for any aspect of cargo tank or cargo acceptance and consequences thereof.

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There are 3 distinct curing states; Full Cure, Post Cure and Hot Cure.
All three states do not always apply to all coatings.

Full Cure
This applies to all coatings mentioned in the resistance list and is the minimum curing time required for carriage of non aggressive cargoes (cargoes without notes 4, 7, 8 and/or 11). These minimum times are detailed in the curing tables found in the data sheets of the respective products. For SigmaGuard 750 (Sigma SilGuard MC), the full cure is the same as for full resistance and no further curing is required for service.

Post Cure
This applies to Sigma PhenGuard, Sigma NovaGuard and SigmaGuard 720 (SigmaGuard EHB) and relates to carriage of aggressive cargoes (cargoes with notes 4, 7, 8 and/or 11). Before carriage of aggressive cargoes, a full cure is required followed by 3 months service (also see Note 4) after which the following is allowed:

Sigma PhenGuard
Carriage of all acceptable aggressive cargoes (cargoes with notes 4, 7, 8 and/or 11) suitable for Sigma PhenGuard, with the exception of Methanol and Vinyl Acetate Monomer which both require a hot cure before carriage.

Sigma NovaGuard
Carriage of all aggressive cargoes (cargoes with notes 4, 7, 8 and/or 11) suitable for Sigma NovaGuard.

SigmaGuard 720 (SigmaGuard EHB)
Carriage of all aggressive cargoes (cargoes with notes 4, 7, 8 and/or 11) suitable for SigmaGuard 720 (SigmaGuard EHB).

Hot Cure
This is only applicable for Sigma PhenGuard and only a requirement when Methanol or Vinyl Acetate Monomer are to be carried. However, to obtain maximum resistance in the shortest possible time a hot cure is generally recommended.

Prior to the hot cure, in all cases, the full cure must have already been achieved.

For double hull vessels, hot curing can be carried out using hot water and the butterworth system as detailed in the Appendix of system sheet 3322. Also see Note 4.

Appendix to Sigma PhenGuard Tank Coating System – Hot Cure (system sheet 3322) Method: Hot Water using Butterworth Systems

For vessels of double hull construction the procedure for hot cure of the Phenguard system with hot (sea) water gives good results.
Temperature of the water: approximately 80 - 85 Degrees Centigrade.

Steel Temperature
Minimum steel temperature of the internal surface must be a constant 60 Degrees Centigrade.

Minimum curing time in relation to steel temperature.

Minimum curing time Steel temperature
16 hours 60 degrees centigrade
 6 hours 70 degrees centigrade
 3 hours 80 degrees centigrade

Recommended procedure is to commence by heating up the water to a temperature of 80 - 85 Degrees Centigrade using heating coils in the slop tanks or by other means such as heat exchangers, then distributing the hot water through butterworths using continuous recirculation method for periods as described in above table.
Start up time before achievement of required substrate temperature depends on the capacity of the heating equipment, and external temperatures.

Special notes
1 - Heating up times are not included in the minimum curing times mentioned in the above table 
2 - Steel temperatures during curing period must be monitored continuously and extensively by  automatic equipment. Special attention to be taken to cold areas, such as but not limited to,  stiffeners etc. A record of temperatures to be maintained at all times. 
3 - To avoid cold wall effect, adjacent areas must be free from cargo or ballast.

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While PPG PMC tank coating systems are resistant to many edible and potable cargoes, PPG PMC shall not bear any responsibility or liability for any odour, taste or contamination imparted to either edible or potable cargoes from the coating or products retained in the coating. It shall be the buyer's and/or user's responsibility (but in any event not the responsibility of PPG PMC), to ensure that any use of the product in connection with the shipping of edible or potable cargoes complies with any appplicable laws under the relevant jurisdictions.

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All references to "gas-free" refer to a steady state gas free condition. The most common value taken for gas free and that recommended by PPG PMC is below the LEL (Lower Explosive Limit) however, the MAC value (Maximum Allowable Concentration) is also sometimes used. For further details on gas-free recommendations and ventilation guidelines see Ventilation. However, this information is only given as a guide and PPG PMC cannot be held responsible for the effectiveness of ventilation procedures.

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The information below is taken from the IMO ‘International Code for the Construction and Equipment of Ships carrying Dangerous Chemicals in Bulk’ (IBC Code 2007 Edition). Please note that IMO should be consulted to confirm the classification. PPG PMC will not accept responsibility for specification changes of cargoes or conditions of transport due to changes in classification by IMO.

Chapter 17 cargoes
Cargoes listed in Chapter 17 of the IBC Code have been evaluated with regard to environmental and safety hazards and subsequently assigned for carriage in vessels meeting a certain design specification. The design criteria for the 3 various ship types 1, 2 and 3 are detailed in the IBC Code and are as follows:

Ship Type 1
A type 1 ship is a chemical tanker intended to transport chapter 17 products with very severe environmental and safety hazards which require maximum preventive measures to preclude an escape of such cargo

Ship Type 2
A type 2 ship is a chemical tanker intended to transport chapter 17 products with appreciably severe environmental and safety hazards which require significant preventive measures to preclude an escape of such cargo. 2(k) denotes that ship type might be subject to regulation 4.1.3 of Annex II of MARPOL 73/78.

Ship Type 3
A type 3 ship is a chemical tanker intended to transport chapter 17 products with sufficiently severe environmental and safety hazards which require a moderate degree of containment to increase survival capability in a damaged condition.

Chapter 18 cargoes (denoted by a * in the IMO column)
Chapter 18 chemicals are those which have been reviewed for their safety and pollution hazards and determined not to present hazards to such an extent as to warrant application of the IBC Code.

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After carriage of alkaline cargoes, wash water generated by tank cleaning operations will be alkaline. The wash water residues must be completely removed and not left in the tanks or loading pipes.

Although the organic coatings themselves are resistant to several inorganic acids in various concentrations, PPG PMC cannot accept these chemicals as cargoes. This being due to the very serious pitting of the steel and undercutting of the coating system that can be caused by the inorganic acid, in areas of damage to the applied system.

SigmaGuard 750 (Sigma SilGuard MC) and other zinc silicate coatings, are not resistant to acids or alkalis. Their suitability is limited to products in the pH-range between 5,5 to 9. The use of acidic or alkaline tank cleaning products must also be avoided.

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METHANOL AND ETHANOL – Regular transport of,
For regular transport of Methanol and Ethanol, SigmaGuard 750 (Sigma SilGuard MC) coated tanks are recommended.

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A non aggressive cargo is defined as a cargo detailed in the resistance list which is not accompanied by any of the following notes: Note 4, Note 7, Note 8, and/or Note 11.
Conversely, cargoes with any of the above notes are considered to be aggressive cargoes.

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All the tanks to be repaired must be cleaned by means of high pressure washing (H.P.W.) with fresh water using detergent, to remove any oil, grease, cargo residue etc., and chlorides, if needed. The tanks then have to be dried before any preparation can start.

Damages should be separated into the following areas:

  1. Corrosion spots on flat surfaces and edges of frames
  2. Corrosion spots on / in welds
  3. Detachment of topcoat
  4. Low dft

The following recommendations can be given per area:

  1. Sandpapering till sound surface and abrading adjacent areas to obtain ‘key’ for adhesion
  2. Vacuum- or baby blast till Sa2,5 and abrading adjacent area to obtain ‘key’ for adhesion
  3. Sandpapering to obtain ‘key’ for adhesion
  4. Sandpapering to obtain ‘key’ for adhesion

System areas 1 & 2:
As the areas involved are very small, we would recommend SigmaGuard 795 for the repair of an epoxy tank coating as this product can be applied by brush in a 2 or 3 coat system.

System area 3:
Apply by means of airless spray one coat of 100 microns.

System area 4:
Apply one coat of SigmaGuard 795 by brush, for repair of epoxy tank coatings.

Curing for all areas according to the respective data sheets.

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The first coat of the system must be applied directly to the steel substrate which has been blasted in-situ to a minimum of ISO-Sa 2½, free from rust, scale, water soluble salts and other foreign matter. Application of the systems must be carried out in accordance with the respective product data and system sheets. After application of the full system has been completed, the system has to be cured under specified conditions for at least the minimum period indicated in the system and product data sheets.

Exposure of the coating to an aggressive cargo before the coating has obtained full cure, may permanently damage the resistance properties of the system. To obtain maximum resistance in the shortest possible time a hot post cure is recommended.

This list is not valid when shop primers are present under the coating system. Shop primers must be completely removed.

When part of the structure is of stainless steel, the blasting profile of the stainless steel substrate should be the same as for mild steel. Please refer to the respective system and product data sheets.

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A synonym is another name for the same chemical or composition. One chemical can have a number of different names or synonyms, e.g. Methyl Alcohol is a synonym for Methanol.

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Whilst a list of tank cleaning chemicals suitable for use with our tank coatings is available, PPG PMC does not advise on specific tank cleaning procedures or regimes. For detailed advice on this subject we recommend contacting one of the specialist tank cleaning companies.

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Generally cargoes are stored and transported at ambient temperatures up to 35°C.

For highly viscous cargoes, maximum storage temperatures are indicated in °C. Loading and discharge temperatures may be up to 10 °C higher. However the period for which the cargo is kept at these higher temperatures should be kept as short as possible and must not exceed 48 hours.

The temperature to which high viscosity cargoes have to be raised for loading and discharging have been obtained from organisations engaged in the transport and manufacture of such chemicals.

For less viscous cargoes, which do not require heating to reduce viscosity, no maximum temperatures are stated. This means that for these cargoes no higher temperatures are allowed than those occurring in world-wide storage or transport under ambient conditions. For cargo temperatures above 35 °C PPG PMC should be consulted.

Cargoes in this list with reference notes 4, 7, 8 and/or 11 should not be carried in tanks adjacent to those containing cargoes having higher temperatures than allowed for these specific cargoes.

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The resistance code refers to bulk storage or transport of cargoes for a maximum period of 6 months unless a shorter time is specified. For extended storage or transport times PPG PMC must be consulted.

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VENTILATION - TRIS List ventilation guidelines for cargoes with notes 4, 7, 8 and/or 11.
In order to extend the service life of the coating, after carriage of cargoes with notes 4, 7, 8 and/or 11 and before carriage of another cargo or water contact, it is necessary to allow release of absorbed cargo by fully ventilating the tank followed by carriage of a non aggressive cargo for at least 10 days. The measures detailed below are given as a guideline for a suitable ventilation procedure, they should not be interpreted as a comprehensive set of instructions for every vessel as the requirements and procedures vary from vessel to vessel and are dependant on / influenced by such things as cargo carried, tank size, tank configuration, pump capacity, ambient temperature, relative humidity etc.

These guidelines are also not intended to have priority over any local, national or international rules or laws.

  1. After complete* discharge of cargo, the tank should be ventilated until gas free. The most common value taken for gas free and that recommended by PPG PMC is 1% of the LEL (Lower Explosive Limit) however, the MAC value (Maximum Allowable Concentration) is also sometimes used. The gas concentration should be measured at different levels and different locations.
  2. After the tank has been made gas free it should then be ventilated for at least 24 hours.

    There are two main methods for ventilation, dilution and displacement. Dilution is the least efficient method and involves blowing air into the tank at the top thereby forcing air out through other tank openings. Here the dilution is very slow and inefficient, with gas pockets likely to remain in the bottom corners of the tank etc.

    Displacement is by far the quickest being, most efficient method for ventilation and is therefore strongly recommended. For cargo vapours heavier than air (most cargoes), these heavy vapours settle on the tank bottom and should be extracted by means of an extraction fan connected to flexible trunking which is lowered into the tank until just above the tank bottom. It is strongly recommended to reposition the flexible trunking during extraction/ventilation. Fresh/dry air, to replace the extracted vapours, should simultaneously be allowed to enter the tank through fully opened tank covers, sampling holds and butterworth lids in the top of the tank.

    It is important to prevent condensation forming on the paint film and therefore the relative humidity of the air used should be kept as low as possible. Under normal circumstances use of the heating coils during ventilation is strongly advised, as it reduces the risk of condensation forming on the paint film and will accelerate desorbtion of the cargo.
  3. After ventilation has been carried out, the tank should be closed for 8 - 12 hours and then opened and measured to see if it is gas free (1% of the f LEL) as due to release of absorbed cargo during this period, the gas concentration could have increased above the specified limit and therefore further ventilation is required.)

    1. If gas free, then the tank is suitable for loading of a non-aggressive cargo.
    2. If not gas free, then the ventilation procedure detailed in 2) should be repeated and thereafter the tank should be measured to see if it is gas free (1% of the LEL).

    The following points are general and apply for all ventilation processes:
  4. Ambient air with a high relative humidity (such as that found during adverse weather conditions - mist, rain, spray etc.) should not be used for any ventilation process.
  5. All times quoted are for an ambient temperature of 20°C.
  6. Tank size and configuration play an important role and it is advisable, if possible, to reposition the flexible trunking and fan periodically in such a way that gas pockets are avoided.
  7. Air used for tank ventilation should not be recirculated.

*Complete discharge of cargo means that no residual cargo should be present on the tank bottom, in the by-pass pump, the  stripping line, the drop line and that the deep-well pump must be completely emptied.

The above procedure does not guarantee complete removal of absorbed cargo from the coating and is provided as a guide only. Further guidance on tank ventilation and safety matters can be found in the International Safety Guide for Oil Tankers & Terminals (ISGOTT).

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Zinc pick up by the cargo in tanks coated with SigmaGuard 750 (Sigma SilGuard MC) may occur, depending on the cargo in question.

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