Chemical Pump Materials and Corrosion Resistance

How Corrosion Attacks a Chemical Pump

Corrosion failures rarely look alike, and recognising the damage mode helps the engineer choose both the material and the pump configuration:

• Uniform corrosion — even surface wasting; choose a material with a low corrosion rate in the medium.
• Pitting and crevice corrosion — localised attack at defects, under deposits or at gaskets; typical of chlorides on hot stainless steel.
• Galvanic corrosion — dissimilar wetted metals in a conductive liquid form a cell; the less noble one corrodes faster.
• Stress corrosion cracking — tensile stress plus chlorides at temperature cracks an otherwise intact alloy.
• Erosion-corrosion — fast flow or suspended solids strip the protective film and speed up attack.

Stainless Steel Wetted Parts: SS304 and SS316L

Austenitic stainless steels are the default wetted material for the IH series, combining corrosion resistance with strength and cleanability. SS304 is the economical general-purpose grade for mild chemicals, dilute acids and alkalis and salt solutions. SS316L adds molybdenum, markedly improving resistance to pitting and crevice corrosion in chloride-bearing media such as brine. Both have limits — hot concentrated acids and strong oxidising chlorides attack them — hence the IH series rating of 80°C for mild chemicals and dilute acids or alkalis.

Fluoroplastic Linings: PTFE, FEP and PFA

When a chemical attacks stainless steel, the economical answer is often a lined pump rather than an exotic alloy. The IHF series protects the metal casing with a fluoroplastic lining — PTFE, FEP or PFA — which resists a broad range of aggressive media, including strong acids such as sulfuric, hydrochloric, hydrofluoric and nitric acid, strong alkalis and oxidising agents, at service temperatures up to 100°C. PFA and FEP are melt-processable grades, while PTFE offers the classic extreme chemical resistance. Fluoroplastics are not indestructible — some small molecules permeate the lining slowly — so verify the chemical, concentration and temperature against the compatibility chart (see chemical pump selection based on fluid properties.

Every Wetted Component Must Be Compatible

A lined casing does not make the whole pump corrosion-proof: the impeller, shaft sleeve and seal faces also contact the liquid. The mechanical seal — available single or double — is the most leak-critical point, and its faces and elastomers must suit the chemical and temperature. A common mistake is checking only the casing while the seal elastomer degrades in the liquid; double seals with a barrier fluid serve where leakage must be fully contained.

Concentration and Temperature Change the Corrosion Picture

Concentration and temperature decide corrosion: a chemical harmless when dilute can be aggressive when concentrated or hot — dilute sulfuric acid is a routine stainless duty while hot concentrated acid attacks most metals. Hence the IH family is limited to dilute acids and alkalis at 80°C and the IHF family extends strong-acid, strong-alkali and oxidising service to 100°C. State the normal and maximum temperatures and the full concentration range so the engineer judges the worst case, not the average. A complete method for turning the fluid profile into a specification is given in our chemical transfer pump selection guide.

Corrosion-Resistant Selection Checks

• Name the chemical and its concentration — impurities included, since trace chlorides or oxidisers change the material answer.
• State the temperature limits — normal and maximum; corrosion rates rise sharply with temperature.
• Check every wetted component — casing, impeller, shaft sleeve, seal faces and elastomers, not just the headline material.
• Avoid galvanic couples — keep dissimilar wetted metals compatible in the conductive liquid.
• Verify against the compatibility chart — and confirm the final selection with the manufacturer for the current IH/IHF chemical pump range.

Frequently Asked Questions