Sigma TankSelect uses following features for chemical resistance suitability of the coating system:
Maximum temperature in degrees Centigrade (T)
||When no resistance note is stated, no
||information is available on resistance
1, 2, 3 etc.
|Suitable subject to reference notes 1, 2, 3 etc.
T ( °C)
|Suitable up to T degrees Centegrade
For highly viscous cargoes, maximum storage temperatures are indicated in degrees Centigrade. Loading and discharge temperatures may be up to 10 degrees Centigrade higher. But 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 organizations 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 under ambient conditions. For cargo temperatures above 35°C PPG PMC should be consulted.
Cargoes in this list with reference notes 4, 7, 8 or 11 should not be stored in tanks adjacent to those containing cargoes having higher temperatures than allowed for these specific cargoes.
Cargo and product conformity
This list is based on practical tests carried out on pure and/or commercial products. The composition of many commercial products contained in this 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.
Non-listed cargoes and temperature deviations
For cargoes not included in this list or cargoes without resistance indications or when deviating from maximum temperatures, PPG PMC must be consulted before such a cargo is accepted or stored.
Inorganic acids and alkalis
After storage 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 is 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 mechanical or other forms of damage to the applied system.
SigmaGuard 750 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.
Edible and Potable Cargoes
While PPG PMC tanklining 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. For land storage tanks where either edible or potable cargoes will be stored, the buyer must ensure that the proposed tanklining system complies with local regulation for the storage of food stuff.
Absorption of cargo by the coating may occur and subsequent desorption is dependant on such factors as temperature, ventilation, humidity, absorbed species and 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 could be important 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 dedicated storage the client carries out testing of cured panels of the chosen coating in contact with the cargo in question first 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 the 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.
Regular or continuous storage of methanol and ethanol
For regular or continuous storage of methanol and ethanol, SigmaGuard 750 coated tanks are recommended.
There are 3 distinct curing states; Full Cure, Post Cure and Hot Cure.
All three states do not always apply to all coatings.
1. Full Cure
This applies to all coatings mentioned in the resistance list and is the minimum curing time required for storage 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, the full cure is the same as for full resistance and no further curing is required for service.
2. Post Cure
This applies to SigmaGuard 720, SigmaGuard 730, SigmaGuard 790, SigmaGuard CSF 650, NovaGuard 840, NovaGuard 890, PhenGuard and relates to storage of aggressive cargoes (cargoes with notes 4, 7, 8 and/or 11). Before storage of aggressive cargoes, a full cure is required followed by 3 months service after which the following is allowed:
2a. SigmaGuard 720, SigmaGuard 730 and SigmaGuard 790
Storage of all aggressive cargoes (cargoes with notes 4, 7, 8 and/or 11) suitable for SigmaGuard 720, SigmaGuard 730 and SigmaGuard 790.
2b. SigmaGuard CSF 650
Storage of all aggressive cargoes (cargoes with notes 4, 7, 8 and/or 11) suitable for SigmaGuard CSF 650.
2c. NovaGuard 840 and NovaGuard 890
Storage of all aggressive cargoes (cargoes with notes 4, 7, 8 and/or 11) suitable for NovaGuard 840 and NovaGuard 890.
Storage of all acceptable aggressive cargoes (cargoes with notes 4, 7, 8 and/or 11) suitable for PhenGuard, with the exception of Methanol and Vinyl Acetate Monomer which both require a hot cure before storage.
This is only applicable for PhenGuard and only a requirement when Methanol or Vinyl Acetate Monomer is 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.
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
- Heating up times are not included in the minimum curing times mentioned in the above table
- Steel temperatures during curing period must be monitored continuously and extensively by automatic equipment. Special attention to be taken to cold areas and a record of temperatures is to be maintained at all times.
Zinc pick up
Zinc pick up by the cargo in tanks coated with SigmaGuard 750 may occur, depending on the cargo in question.
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.
Whilst a list of tank cleaning chemicals suitable for use with our tank coatings is available on request, 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 companies.
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 LEL (Lower Explosive Limit), but the MAC value (Maximum Allowable Concentration) is also sometimes used. For further details on ‘gas free’ recommendations and ventilation guidelines (see also information sheet 1434). However, this information is only given as a guide and PPG PMC cannot be held responsible for the effectiveness of ventilation procedures.