Which of the following is not a major factor associated with corrosion by sulfidation?

The severity of hydrochloric acid corrosion ________ with _________ HCl concentration and increasing temperatures.

Amine stress corrosion cracking is most often associated with lean amine services. The pure alkanolamine does not cause cracking. Cracking in rich amine services are most often associated with _______ problems.

Increasing the chromium in steels offers no major improvement in resistance to CO² corrosion until a minimum of __________ is reached.

Carbonate stress corrosion cracking usually occurs at welds or cold worked areas that __________.